René Descartes is often credited with being the “Father of Modern Philosophy.” This title is justified due both to his break with the traditional Scholastic-Aristotelian philosophy prevalent at his time and to his development and promotion of the new, mechanistic sciences. His fundamental break with Scholastic philosophy was twofold. First, Descartes thought that the Scholastics’ method was prone to doubt given their reliance on sensation as the source for all knowledge. Second, he wanted to replace their final causal model of scientific explanation with the more modern, mechanistic model.
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Descartes attempted to address the former issue via his method of doubt. His basic strategy was to consider false any belief that falls prey to even the slightest doubt. This “hyperbolic doubt” then serves to clear the way for what Descartes considers to be an unprejudiced search for the truth. This clearing of his previously held beliefs then puts him at anepistemological ground-zero. From here Descartes sets out to find something that lies beyond all doubt.
He eventually discovers that “I exist” is impossible to doubt and is, therefore, absolutely certain. It is from this point that Descartes proceeds to demonstrate God’s existence and that God cannot be a deceiver.
This, in turn, serves to fix the certainty of everything that is clearly and distinctly understood and provides the epistemological foundation Descartes set out to find. Once this conclusion is reached, Descartes can proceed to rebuild his system of previously dubious beliefs on this absolutely certain foundation. These beliefs, which are re-established with absolute certainty, include the existence of a world of bodies external to the mind, the dualistic distinction of the immaterial mind from the body, and his mechanistic model of physics based on the clear and distinct ideas of geometry. This points toward his second, major break with the Scholastic Aristotelian tradition in that Descartes intended to replace their system based on final causal explanations with his system based on mechanistic principles. Descartes also applied this mechanistic framework to the operation of plant, animal and human bodies, sensation and the passions. All of this eventually culminating in a moral system based on the notion of “generosity.” The Modern Turn
a. Against Scholasticism
Descartes is often called the “Father of Modern Philosophy,” implying that he provided the seed for a new philosophy that broke away from the old in important ways. This “old” philosophy is Aristotle’s as it was appropriated and interpreted throughout the later medieval period. In fact, Aristotelianism was so entrenched in the intellectual institutions of Descartes’ time that commentators argued that evidence for its the truth could be found in the Bible. Accordingly, if someone were to try to refute some main Aristotelian tenet, then he could be accused of holding a position contrary to the word of God and be punished. However, by Descartes’ time, many had come out in some way against one Scholastic-Aristotelian thesis or other. So, when Descartes argued for the implementation of his modern system of philosophy, breaks with the Scholastic tradition were not unprecedented. Descartes broke with this tradition in at least two fundamental ways. The first was his rejection of substantial forms as explanatory principles in physics. A substantial form was thought to be an immaterial principle of material organization that resulted in a particular thing of a certain kind. The main principle of substantial forms was the final cause or purpose of being that kind of thing.
For example, the bird called the swallow. The substantial form of “swallowness” unites with matter so as to organize it for the sake of being a swallow kind of thing. This also means that any dispositions or faculties the swallow has by virtue of being that kind of thing is ultimately explained by the goal or final cause of being a swallow. So, for instance, the goal of being a swallow is the cause of the swallow’s ability to fly. Hence, on this account, a swallow flies for the sake of being a swallow. Although this might be true, it does not say anything new or useful about swallows, and so it seemed to Descartes that Scholastic philosophy and science was incapable of discovering any new or useful knowledge. Descartes rejected the use of substantial forms and their concomitant final causes in physics precisely for this reason. Indeed, his essay Meteorology, that appeared alongside the Discourse on Method, was intended to show that clearer and more fruitful explanations can be obtained without reference to substantial forms but only by way of deductions from the configuration and motion of parts.
Hence, his point was to show that mechanistic principles are better suited for making progress in the physical sciences. Another reason Descartes rejected substantial forms and final causes in physics was his belief that these notions were the result of the confusion of the idea of the body with that of the mind. In theSixth Replies, Descartes uses the Scholastic conception of gravity in a stone, to make his point. On this account, a characteristic goal of being a stone was a tendency to move toward the center of the earth. This explanation implies that the stone has knowledge of this goal, of the center of the earth and of how to get there. But how can a stone know anything, since it does not think? So, it is a mistake to ascribe mental properties like knowledge to entirely physical things. This mistake should be avoided by clearly distinguishing the idea of the mind from the idea of the body. Descartes considered himself to be the first to do this. His expulsion of the metaphysical principles of substantial forms and final causes helped clear the way for Descartes’ new metaphysical principles on which his modern, mechanistic physics was based.
The second fundamental point of difference Descartes had with the Scholastics was his denial of the thesis that all knowledge must come from sensation. The Scholastics were devoted to the Aristotelian tenet that everyone is born with a clean slate, and that all material for intellectual understanding must be provided through sensation. Descartes, however, argued that since the senses sometimes deceive, they cannot be a reliable source for knowledge. Furthermore, the truth of propositions based on sensation is naturally probabilistic and the propositions, therefore, are doubtful premises when used in arguments. Descartes was deeply dissatisfied with such uncertain knowledge. He then replaced the uncertain premises derived from sensation with the absolute certainty of the clear and distinct ideas perceived by the mind alone, as will be explained below. b. Descartes’ Project
In the preface to the French edition of the Principles of Philosophy, Descartes uses a tree as a metaphor for his holistic view of philosophy. “The roots are metaphysics, the trunk is physics, and the branches emerging from the trunk are all the other sciences, which may be reduced to three principal ones, namely medicine, mechanics and morals” (AT IXB 14: CSM I 186). Although Descartes does not expand much more on this image, a few other insights into his overall project can be discerned. First, notice that metaphysics constitutes the roots securing the rest of the tree. For it is in Descartes’ metaphysics where an absolutely certain and secure epistemological foundation is discovered.
This, in turn, grounds knowledge of the geometrical properties of bodies, which is the basis for his physics. Second, physics constitutes the trunk of the tree, which grows up directly from the roots and provides the basis for the rest of the sciences. Third, the sciences of medicine, mechanics and morals grow out of the trunk of physics, which implies that these other sciences are just applications of his mechanistic science to particular subject areas. Finally, the fruits of the philosophy tree are mainly found on these three branches, which are the sciences most useful and beneficial to humankind. However, an endeavor this grand cannot be conducted haphazardly but should be carried out in an orderly and systematic way. Hence, before even attempting to plant this tree, Descartes must first figure out a method for doing so. Method
Aristotle and subsequent medieval dialecticians set out a fairly large, though limited, set of acceptable argument forms known as “syllogisms” composed of a general or major premise, a particular or minor premise and a conclusion. Although Descartes recognized that these syllogistic forms preserve truth from premises to conclusion such that if the premises are true, then the conclusion must be true, he still found them faulty. First, these premises are supposed to be known when, in fact, they are merely believed, since they express only probabilities based on sensation. Accordingly, conclusions derived from merely probable premises can only be probable themselves, and, therefore, these probable syllogisms serve more to increase doubt rather than knowledge Moreover, the employment of this method by those steeped in the Scholastic tradition had led to such subtle conjectures and plausible arguments that counter-arguments were easily constructed, leading to profound confusion. As a result, the Scholastic tradition had become such a confusing web of arguments, counter-arguments and subtle distinctions that the truth often got lost in the cracks. (Rules for the Direction of the Mind, AT X 364, 405-406 & 430: CSM I 11-12, 36 & 51-52).
Descartes sought to avoid these difficulties through the clarity and absolute certainty of geometrical-style demonstration. In geometry, theorems are deduced from a set of self-evident axioms and universally agreed upon definitions. Accordingly, direct apprehension of clear, simple and indubitable truths (or axioms) by intuition and deductions from those truths can lead to new and indubitable knowledge. Descartes found this promising for several reasons. First, the ideas of geometry are clear and distinct, and therefore they are easily understood unlike the confused and obscure ideas of sensation. Second, the propositions constituting geometrical demonstrations are not probabilistic conjectures but are absolutely certain so as to be immune from doubt. This has the additional advantage that any proposition derived from some one or combination of these absolutely certain truths will itself be absolutely certain. Hence, geometry’s rules of inference preserve absolutely certain truth from simple, indubitable and intuitively grasped axioms to their deductive consequences unlike the probable syllogisms of the Scholastics. The choice of geometrical method was obvious for Descartes given his previous success in applying this method to other disciplines like optics.
Yet his application of this method to philosophy was not unproblematic due to a revival of ancient arguments for global or radical skepticism based on the doubtfulness of human reasoning. But Descartes wanted to show that truths both intuitively grasped and deduced are beyond this possibility of doubt. His tactic was to show that, despite the best skeptical arguments, there is at least one intuitive truth that is beyond all doubt and from which the rest of human knowledge can be deduced. This is precisely the project of Descartes’ seminal work, Meditations on First Philosophy. In the First Meditation, Descartes lays out several arguments for doubting all of his previously held beliefs. He first observes that the senses sometimes deceive, for example, objects at a distance appear to be quite small, and surely it is not prudent to trust someone (or something) that has deceived us even once. However, although this may apply to sensations derived under certain circumstances, doesn’t it seem certain that “I am here, sitting by the fire, wearing a winter dressing gown, holding this piece of paper in my hands, and so on”? (AT VII 18: CSM II 13).
Descartes’ point is that even though the senses deceive us some of the time, what basis for doubt exists for the immediate belief that, for example, you are reading this article? But maybe the belief of reading this article or of sitting by the fireplace is not based on true sensations at all but on the false sensations found in dreams. If such sensations are just dreams, then it is not really the case that you are reading this article but in fact you are in bed asleep. Since there is no principled way of distinguishing waking life from dreams, any belief based on sensation has been shown to be doubtful. This includes not only the mundane beliefs about reading articles or sitting by the fire but even the beliefs of experimental science are doubtful, because the observations upon which they are based may not be true but mere dream images. Therefore, all beliefs based on sensation have been called into doubt, because it might all be a dream. This, however, does not pertain to mathematical beliefs, since they are not based on sensation but on reason. For even though one is dreaming, for example, that, 2 + 3 = 5, the certainty of this proposition is not called into doubt, because 2 + 3 = 5 whether the one believing it is awake or dreaming.
Descartes continues to wonder about whether or not God could make him believe there is an earth, sky and other extended things when, in fact, these things do not exist at all. In fact, people sometimes make mistakes about things they think are most certain such as mathematical calculations. But maybe people are not mistaken just some of the time but all of the time such that believing that 2 + 3 = 5 is some kind of persistent and collective mistake, and so the sum of 2 + 3 is really something other than 5. However, such universal deception seems inconsistent with God’s supreme goodness. Indeed, even the occasional deception of mathematical miscalculation also seems inconsistent with God’s goodness, yet people do sometimes make mistakes. Then, in line with the skeptics, Descartes supposes, for the sake of his method, that God does not exist, but instead there is an evil demon with supreme power and cunning that puts all his efforts into deceiving him so that he is always mistaken about everything, including mathematics.
In this way, Descartes called all of his previous beliefs into doubt through some of the best skeptical arguments of his day But he was still not satisfied and decided to go a step further by considering false any belief that falls prey to even the slightest doubt. So, by the end of the First Meditation, Descartes finds himself in a whirlpool of false beliefs. However, it is important to realize that these doubts and the supposed falsehood of all his beliefs are for the sake of his method: he does not really believe that he is dreaming or is being deceived by an evil demon; he recognizes that his doubt is merely hyperbolic. But the point of this “methodological” or ‘hyperbolic” doubt is to clear the mind of preconceived opinions that might obscure the truth. The goal then is to find something that cannot be doubted even though an evil demon is deceiving him and even though he is dreaming. This first indubitable truth will then serve as an intuitively grasped metaphysical “axiom” from which absolutely certain knowledge can be deduced. For more, see Cartesian skepticism. The Mind
a. Cogito, ergo sum
In the Second Meditation, Descartes tries to establish absolute certainty in his famous reasoning: Cogito, ergo sum or “I think, therefore I am.” These Meditations are conducted from the first person perspective, from Descartes.’ However, he expects his reader to meditate along with him to see how his conclusions were reached. This is especially important in the Second Meditation where the intuitively grasped truth of “I exist” occurs. So the discussion here of this truth will take place from the first person or “I” perspective. All sensory beliefs had been found doubtful in the previous meditation, and therefore all such beliefs are now considered false. This includes the belief that I have a body endowed with sense organs. But does the supposed falsehood of this belief mean that I do not exist?
No, for if I convinced myself that my beliefs are false, then surely there must be an “I” that was convinced. Moreover, even if I am being deceived by an evil demon, I must exist in order to be deceived at all. So “I must finally conclude that the proposition, ‘I am,’ ‘I exist,’ is necessarily true whenever it is put forward by me or conceived in my mind” (AT VII 25: CSM II 16-17). This just means that the mere fact that I am thinking, regardless of whether or not what I am thinking is true or false, implies that there must be something engaged in that activity, namely an “I.” Hence, “I exist” is an indubitable and, therefore, absolutely certain belief that serves as an axiom from which other, absolutely certain truths can be deduced. b. The Nature of the Mind and its Ideas
The Second Meditation continues with Descartes asking, “What am I?” After discarding the traditional Scholastic-Aristotelian concept of a human being as a rational animal due to the inherent difficulties of defining “rational” and “animal,” he finally concludes that he is a thinking thing, a mind: “A thing that doubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sense perceptions” (AT VII 28: CSM II 19). In the Principles, part I, sections 32 and 48, Descartes distinguishes intellectual perception and volition as what properly belongs to the nature of the mind alone while imagination and sensation are, in some sense, faculties of the mind insofar as it is united with a body. So imagination and sensation are faculties of the mind in a weaker sense than intellect and will, since they require a body in order to perform their functions. Finally, in the Sixth Meditation, Descartes claims that the mind or “I” is a non-extended thing.
Now, since extension is the nature of body, is a necessary feature of body, it follows that the mind is by its nature not a body but an immaterial thing. Therefore, what I am is an immaterial thinking thing with the faculties of intellect and will. It is also important to notice that the mind is a substance and the modes of a thinking substance are its ideas. For Descartes a substance is a thing requiring nothing else in order to exist. Strictly speaking, this applies only to God whose existence is his essence, but the term “substance” can be applied to creatures in a qualified sense. Minds are substances in that they require nothing except God’s concurrence, in order to exist. But ideas are “modes” or “ways” of thinking, and, therefore, modes are not substances, since they must be the ideas of some mind or other. So, ideas require, in addition to God’s concurrence, some created thinking substance in order to exist (see Principles of Philosophy, part I, sections 51 & 52). Hence the mind is an immaterial thinking substance, while its ideas are its modes or ways of thinking. Descartes continues on to distinguish three kinds of ideas at the beginning of the Third Meditation, namely those that are fabricated, adventitious, or innate. Fabricated ideas are mere inventions of the mind.
Accordingly, the mind can control them so that they can be examined and set aside at will and their internal content can be changed. Adventitious ideas are sensations produced by some material thing existing externally to the mind. But, unlike fabrications, adventitious ideas cannot be examined and set aside at will nor can their internal content be manipulated by the mind. For example, no matter how hard one tries, if someone is standing next to a fire, she cannot help but feel the heat as heat. She cannot set aside the sensory idea of heat by merely willing it as we can do with our idea of
Santa Claus, for example. She also cannot change its internal content so as to feel something other than heat–say, cold. Finally, innate ideas are placed in the mind by God at creation. These ideas can be examined and set aside at will but their internal content cannot be manipulated. Geometrical ideas are paradigm examples of innate ideas. For example, the idea of a triangle can be examined and set aside at will, but its internal content cannot be manipulated so as to cease being the idea of a three-sided figure. Other examples of innate ideas would be metaphysical principles like “what is done cannot be undone,” the idea of the mind, and the idea of God.
Descartes’ idea of God will be discussed momentarily, but let’s consider his claim that the mind is better known than the body. This is the main point of the wax example found in the Second Meditation. Here, Descartes pauses from his methodological doubt to examine a particular piece of wax fresh from the honeycomb: It has not yet quite lost the taste of the honey; it retains some of the scent of flowers from which it was gathered; its color shape and size are plain to see; it is hard, cold and can be handled without difficulty; if you rap it with your knuckle it makes a sound. (AT VII 30: CSM II 20) The point is that the senses perceive certain qualities of the wax like its hardness, smell, and so forth. But, as it is moved closer to the fire, all of these sensible qualities change. “Look: the residual taste is eliminated, the smell goes away, the color changes, the shape is lost, the size increases, it becomes liquid and hot” (AT VII 30: CSM II 20). However, despite these changes in what the senses perceive of the wax, it is still judged to be the same wax now as before. To warrant this judgment, something that does not change must have been perceived in the wax. This reasoning establishes at least three important points. First, all sensation involves some sort of judgment, which is a mental mode.
Accordingly, every sensation is, in some sense, a mental mode, and “the more attributes [that is, modes] we discover in the same thing or substance, the clearer is our knowledge of that substance” (AT VIIIA 8: CSM I 196). Based on this principle, the mind is better known than the body, because it has ideas about both extended and mental things and not just of extended things, and so it has discovered more modes in itself than in bodily substances. Second, this is also supposed to show that what is unchangeable in the wax is its extension in length, breadth and depth, which is not perceivable by the senses but by the mind alone.
The shape and size of the wax are modes of this extension and can, therefore, change. But the extension constituting this wax remains the same and permits the judgment that the body with the modes existing in it after being moved by the fire is the same body as before even though all of its sensible qualities have changed. One final lesson is that Descartes is attempting to wean his reader from reliance on sense images as a source for, or an aid to, knowledge. Instead, people should become accustomed to thinking without images in order to clearly understand things not readily or accurately represented by them, for example, God and the mind. So, according to Descartes, immaterial, mental things are better known and, therefore, are better sources of knowledge than extended things. God
a. The Causal Arguments
At the beginning of the Third Meditation only “I exist” and “I am a thinking thing” are beyond doubt and are, therefore, absolutely certain. From these intuitively grasped, absolutely certain truths, Descartes now goes on to deduce the existence of something other than himself, namely God. Descartes begins by considering what is necessary for something to be the adequate cause of its effect. This will be called the “Causal Adequacy Principle” and is expressed as follows: “there must be at least as much reality in the efficient and total cause as in the effect of that cause,” which in turn implies that something cannot come from nothing (AT VII 40: CSM II 28). Here Descartes is espousing a causal theory that implies whatever is possessed by an effect must have been given to it by its cause. For example, when a pot of water is heated to a boil, it must have received that heat from some cause that had at least that much heat. Moreover, something that is not hot enough cannot cause water to boil, because it does not have the requisite reality to bring about that effect. In other words, something cannot give what it does not have.
Descartes goes on to apply this principle to the cause of his ideas. This version of the Causal Adequacy Principle states that whatever is contained objectively in an idea must be contained either formally or eminently in the cause of that idea. Definitions of some key terms are now in order. First, the objective reality contained in an idea is just its representational content; in other words, it is the “object” of the idea or what that idea is about. The idea of the sun, for instance, contains the reality of the sun in it objectively. Second, the formal reality contained in something is a reality actually contained in that thing. For example, the sun itself has the formal reality of extension since it is actually an extended thing or body. Finally, a reality is contained in something eminently when that reality is contained in it in a higher form such that (1) the thing does not possess that reality formally, but (2) it has the ability to cause that reality formally in something else. For example, God is not formally an extended thing but solely a thinking thing; however, he is eminently the extended universe in that it exists in him in a higher form, and accordingly he has the ability to cause its existence.
The main point is that the Causal Adequacy Principle also pertains to the causes of ideas so that, for instance, the idea of the sun must be caused by something that contains the reality of the sun either actually (formally) or in some higher form (eminently). Once this principle is established, Descartes looks for an idea of which he could not be the cause. Based on this principle, he can be the cause of the objective reality of any idea that he has either formally or eminently. He is formally a finite substance, and so he can be the cause of any idea with the objective reality of a finite substance. Moreover, since finite substances require only God’s concurrence to exist and modes require a finite substance and God, finite substances are more real than modes. Accordingly, a finite substance is not formally but eminently a mode, and so he can be the cause of all his ideas of modes. But the idea of God is the idea of an infinite substance. Since a finite substance is less real than an infinite substance by virtue of the latter’s absolute independence, it follows that Descartes, a finite substance, cannot be the cause of his idea of an infinite substance.
This is because a finite substance does not have enough reality to be the cause of this idea, for if a finite substance were the cause of this idea, then where would it have gotten the extra reality? But the idea must have come from something. So something that is actually an infinite substance, namely God, must be the cause of the idea of an infinite substance. Therefore, God exists as the only possible cause of this idea. Notice that in this argument Descartes makes a direct inference from having the idea of an infinite substance to the actual existence of God. He provides another argument that is cosmological in nature in response to a possible objection to this first argument. This objection is that the cause of a finite substance with the idea of God could also be a finite substance with the idea of God.
Yet what was the cause of that finite substance with the idea of God? Well, another finite substance with the idea of God. But what was the cause of that finite substance with the idea of God? Well, another finite substance . . . and so on to infinity. Eventually an ultimate cause of the idea of God must be reached in order to provide an adequate explanation of its existence in the first place and thereby stop the infinite regress. That ultimate cause must be God, because only he has enough reality to cause it. So, in the end, Descartes claims to have deduced God’s existence from the intuitions of his own existence as a finite substance with the idea of God and the Causal Adequacy Principle, which is “manifest by the natural light,” thereby indicating that it is supposed to be an absolutely certain intuition as well. b. The Ontological Argument
The ontological argument is found in the Fifth Meditation and follows a more straightforwardly geometrical line of reasoning. Here Descartes argues that God’s existence is deducible from the idea of his nature just as the fact that the sum of the interior angles of a triangle are equal to two right angles is deducible from the idea of the nature of a triangle. The point is that this property is contained in the nature of a triangle, and so it is inseparable from that nature. Accordingly, the nature of a triangle without this property is unintelligible. Similarly, it is apparent that the idea of God is that of a supremely perfect being, that is, a being with all perfections to the highest degree.
Moreover, actual existence is a perfection, at least insofar as most would agree that it is better to actually exist than not. Now, if the idea of God did not contain actual existence, then it would lack a perfection. Accordingly, it would no longer be the idea of a supremely perfect being but the idea of something with an imperfection, namely non-existence, and, therefore, it would no longer be the idea of God. Hence, the idea of a supremely perfect being or God without existence is unintelligible. This means that existence is contained in the essence of an infinite substance, and therefore God must exist by his very nature. Indeed, any attempt to conceive of God as not existing would be like trying to conceive of a mountain without a valley – it just cannot be done.
6. The Epistemological Foundation
a. Absolute Certainty and the Cartesian Circle
Recall that in the First Meditation Descartes supposed that an evil demon was deceiving him. So as long as this supposition remains in place, there is no hope of gaining any absolutely certain knowledge. But he was able to demonstrate God’s existence from intuitively grasped premises, thereby providing, a glimmer of hope of extricating himself from the evil demon scenario. The next step is to demonstrate that God cannot be a deceiver. At the beginning of the Fourth Meditation, Descartes claims that the will to deceive is “undoubtedly evidence of malice or weakness” so as to be an imperfection. But, since God has all perfections and no imperfections, it follows that God cannot be a deceiver. For to conceive of God with the will to deceive would be to conceive him to be both having no imperfections and having one imperfection, which is impossible; it would be like trying to conceive of a mountain without a valley. This conclusion, in addition to God’s existence, provides the absolutely certain foundation Descartes was seeking from the outset of the Meditations.
It is absolutely certain because both conclusions (namely that God exists and that God cannot be a deceiver) have themselves been demonstrated from immediately grasped and absolutely certain intuitive truths. This means that God cannot be the cause of human error, since he did not create humans with a faculty for generating them, nor could God create some being, like an evil demon, who is bent on deception. Rather, humans are the cause of their own errors when they do not use their faculty of judgment correctly. Second, God’s non-deceiving nature also serves to guarantee the truth of all clear and distinct ideas. So God would be a deceiver, if there were a clear and distinct idea that was false, since the mind cannot help but believe them to be true. Hence, clear and distinct ideas must be true on pain of contradiction. This also implies that knowledge of God’s existence is required for having any absolutely certain knowledge. Accordingly, atheists, who are ignorant of God’s existence, cannot have absolutely certain knowledge of any kind, including scientific knowledge. But this veridical guarantee gives rise to a serious problem within the Meditations, stemming from the claim that all clear and distinct ideas are ultimately guaranteed by God’s existence, which is not established until the Third Meditation.
This means that those truths reached in the Second Meditation, such as “I exist” and “I am a thinking thing,” and those principles used in the Third Meditation to conclude that God exists, are not clearly and distinctly understood, and so they cannot be absolutely certain. Hence, since the premises of the argument for God’s existence are not absolutely certain, the conclusion that God exists cannot be certain either. This is what is known as the “Cartesian Circle,” because Descartes’ reasoning seems to go in a circle in that he needs God’s existence for the absolute certainty of the earlier truths and yet he needs the absolute certainty of these earlier truths to demonstrate God’s existence with absolute certainty.
Descartes’ response to this concern is found in the Second Replies. There he argues that God’s veridical guarantee only pertains to the recollection of arguments and not the immediate awaRenéss of an argument’s clarity and distinctness currently under consideration. Hence, those truths reached before the demonstration of God’s existence are clear and distinct when they are being attended to but cannot be relied upon as absolutely certain when those arguments are recalled later on. But once God’s existence has been demonstrated, the recollection of the clear and distinct perception of the premises is sufficient for absolutely certain and, therefore, perfect knowledge of its conclusion (see also the Fifth Meditation at AT VII 69-70: CSM II XXX).