If Descartes had good reasons for thinking that motion is ontologically dependent upon time and for thinking that time is ontologically dependent upon motion, then one might suspect that Descartes will suggest that time and motion are co-dependent (i.e., to have one you must have both). If, however, one returns to Principles I.57, it seems that Descartes rejects this option. In I.57, Descartes argues that duration (a term that he often uses interchangeably with ‘time’) does not depend upon motion for its existence. He argues that the duration of things in motion is the same as the duration of things which are not moving.[5] In claiming that the same duration obtains regardless of motion, Descartes implies that time (or at least duration if there is a distinction) must be ontologically independent of motion. Thus, in I.57, Descartes appears to reject the co-dependency of motion and time. But if he rejects the co-dependency option, then he seems committed to a contradiction—that time both is and is not dependent upon motion for its existence. To determine if Descartes might really hold contradictory views, it seems that one must return to the various passages where he relates the two.
Recall the relationship between time and motion that Descartes gives in Rule 12. In this text, Descartes relates motion with time and duration while explaining the types of conjunction that can exist between simple things.
The conjunction is necessary when one of them is somehow implied (albeit confusedly) in the concept of the other so that we cannot conceive either of them distinctly if we judge them to be separate from each other. It is in this way that shape is conjoined with extension, motion with duration or time, etc. because we cannot conceive of shape which is completely lacking in extension, or a motion wholly lacking in duration.[6]
There are several important points to note in this passage. As already noted, this passage is explicitly discussing an epistemic point (i.e., the requirements for a thing to be conceived). But it seems that Descartes is intentionally making a metaphysical point when explaining what things are necessarily conjoined. For example, Descartes explains that the concept of shape is necessarily conjoined with the concept of extension. The explanation for this epistemic point is a metaphysical fact. One cannot conceive of a shape that lacks extension because shape is a mode of extension—a way that extension is. Without there being a thing that is extended in some way or other, there is no shape. Accordingly, one cannot conceive of shape without extension because this would mean that one was trying to conceive of something that is extended in some way which lacks extension—an impossible being. That we cannot conceive of impossible beings is not a novel claim for Descartes to be making—just as we cannot conceive of square triangles, we cannot conceive of unextended bits of extension. The epistemic limit in these cases is the natural consequent of the metaphysical impossibility of the thing we are trying to conceive. This point is worth noting since it suggests that the other epistemic limit Rule 12 identifies (i.e., that the ideas of duration or time and motion are necessarily conjoined) is one that also makes a metaphysical point and not merely an epistemic one; namely, that time or duration are conceptually dependent on motion because they are metaphysically dependent on motion.
Another interpretive point to note in Rule 12 is that is unclear how the ‘or’ separating duration and time should be interpreted.[7] One might suppose (a) that the ‘or’ distinguishes the duration and time as two different things, both of which are conjoined with motion in the same way, or one might suppose (b) that the ‘or’ indicates that Descartes is speaking loosely and that he uses the terms ‘duration’ and ‘time’ as equivalent ways of picking out the same thing.[8] As (a) and (b) seem to offer equally reasonable interpretations of Rule 12, this passage must be interpreted in light of both possibilities. In other words, this text might be interpreted as claiming either (a) that time and duration are each distinctly dependent on motion, or (b) that time/duration (with each term loosely connoting the same object) depends on motion.
Recall also how Descartes relates time and motion in Principles II.39. In II.39, Descartes claims that “no motion takes place in a single instant of time.”[9] In other words, II.39 suggests the intuitive point that the very possibility of motion requires a succession of moments to ground the possibility of change/motion. The intuitive reasons for supposing that motion depends on some sort of temporal succession have already been discussed. It is worth noting, however, that when Descartes here suggests that motion requires time, he does not thereby exclude time from also being dependent on motion. In claiming that there is no motion at a single instant, Descartes clearly suggests more about the nature of motion than about the nature of time. Accordingly, this passage does not exclude Descartes from holding that some sort of two-way dependence could exist between time and motion. Though it is obviously not the case that there could be a two-way dependence between motion and time if each dependence required the chronological priority of the one before the other,[10] there could be a two-way dependence if motion and time could be jointly and simultaneously dependent—one on the other. Or, a type of two-way dependence could be possible if (as I argue), “time” is a general term that picks out two ontologically distinct entities.
The Real Distinction in Principles I.57
As Principles 1.57 is the most significant passage where Descartes relates time and motion, I will present this passage separately and with particular attention. To do this, I must first address a few interpretive puzzles, and then show how the text explains Descartes’ route for making motion both dependent on time and required for time without assuming a contradiction. Below is the text in its entirety.
Principles 1.57:
Now some attributes or modes are in the very things of which they are said to be attributes or modes, while others are only in our thought. For example, when time is distinguished from duration taken in the general sense and called the measure of movement, it is simply a mode of thought. For the duration which we understand to be involved in movement is certainly no different from the duration involved in things which do not move. This is clear from the fact that if there are two bodies moving for an hour, one slowly and the other quickly, we do not reckon the amount of time to be greater in the latter case than the former, even thought the amount of movement may be much greater. But in order to measure the duration of all things, we compare their duration with the duration of the greatest and most regular motions which give rise to years and days, and we call this duration ‘time’. Yet nothing is thereby added to duration, taken in its general sense, except for a mode of thought.[11]
Some Preliminary Points about Interpreting
Principles I.57
One immediate point to note in this passage is that Descartes claims, “when time is distinguished from duration taken in the general sense and called the measure of movement, it is simply a mode of thought.” As Descartes’ phrasing indicates that he is picking out a special sense of the term ‘time’ (namely, the sense that can be distinguished from duration) it seems that one should not assume that this sense refers to Descartes’ primary notion of time. This should not be assumed since Descartes explicitly states that this special sense only arises when ‘time’ is distinguished from ‘duration,’ which seems to imply that time need not be, or is not always, so distinguished.[12] Given the potential confusion arising from the special sense of ‘time’ that Descartes identifies in I.57, I hereby distinguish this sense from a more general notion of time by labeling this special sense as ‘time-in-thought.’
Another important interpretive point in analyzing Principles I.57 is that Descartes uses both the terms ‘attribute’ and ‘mode’ in this passage, without distinguishing between them. In the previous chapter, I discussed the fact that Descartes offers a technical distinction between principal attributes and modes in Principles I.53.[13] Though Descartes provided this technical distinction just a few pages prior to I.57, Descartes does not seem to be employing the distinction when he uses the terms ‘attribute’ and ‘mode’ in this text. As Descartes is frequently imprec
ise in his use of these terms, this fact is neither very surprising nor noteworthy. In Principles I.55, for example, Descartes himself claims that the concept that he picks out by ‘mode’ in this context is “exactly the same as what is elsewhere meant by an attribute or quality.”[14] Given that Descartes’ is inconsistent in how he uses the terms ‘attribute’ and ‘mode’, whenever these terms appear, one must determine their meaning by reference to the context of their usage. Indeed, since I.57 intends to explain what type of attributes duration and time are (given that some attributes are in things and others are merely in thought), the term ‘attribute’ here cannot refer to a primary attribute of substance. As Descartes identifies a unique primary attribute for physical things (extension) and minds (thinking), he cannot be suggesting that duration and time are additional primary attributes. Rather, it seems that I.57 is just using the term ‘attribute’ to designate a feature of a substance that depends on that substance for its existence, that is, as a way (either essential or nonessential) for a substance to be. According to this usage, it is reasonable for Descartes to use the terms ‘attribute’ and ‘mode’ interchangeably, since both terms pick out this dependent relationship in every context.
There is one more, quick interpretive point to note. In the first sentence of the text, Descartes claims that certain attributes or modes of a substance are in the very substance upon which they depend, while others are only in our thought. As an example of this type of distinction Descartes offers his distinction between duration and time-in-thought. From the fact that Descartes’ explanation assumes that some distinction or other can be drawn between the two attributes, one cannot immediately assume that he is claiming that duration and time-in-thought are two numerically distinct kinds of attributes, since he might just be claiming that duration and time-in-thought are two numerically distinct ways of conceiving of one and the same attribute. In other words, this passage does not explicitly indicate whether Descartes is drawing an ontological or a conceptual distinction between duration and time-in-thought. Moreover, pre-reflectively it might seem as though the distinction is merely a conceptual one. Reading the distinction as conceptual could plausibly be supported by focusing on the interesting “when” that Descartes uses to preface his distinction. In claiming that duration and time-in-thought are only distinguished when one conceives of time in a particularly way (namely, as “the measure of movement”) one might reasonably suppose that the particular way of conceiving of time-in-thought is responsible for the distinction. If the distinction only arose in virtue of a particular way of conceiving, then this would suggest that the relationship between the attributes of duration and time-in-thought could be one of identity—that the only distinction between them arises in virtue of a way of conceiving them. To prove that the distinction between these two attributes is more than just conceptual, one needs to look deeper into Principles I.57—in particular into the different ways that motion relates to each.
Time and Motion in Principles I.57
Immediately after Descartes identifies time-in-thought as the measure of movement, he proceeds to relate motion to duration in particular. He claims that “the duration which we understand to be involved in movement is certainly no different from the duration involved in things which do not move.” As already noted, this claim offers strong evidence against the view that duration (as distinguished from time-in-thought) could bear a very close resemblance to the reductivist’s thesis that time is dependent on motion. If one and the same duration obtains whether or not something is in motion, then it cannot be the case that duration depends on motion, or reduces to a type of motion.
Though I.57 indicates that duration is not dependent on motion, motion’s role for time-in-thought is less clear. There seems to be good reason to anticipate that motion will play a more important role in time-in-thought since Descartes identifies time-in-thought as the “measure of motion” and appeals to the celestial motions to explain it. Descartes claims that the durations of the celestial motions are employed so that the durations of all things can be measured, and then he concludes that “we call this duration ‘time.’”[15] Though Descartes appeals to the cosmic motions to explain how time-in-thought functions, he is not explicit in explaining how time-in-thought actually relates to these motions.
Though Descartes claims that the cosmic motions are used to measure all durations via a comparison, he does not explicitly state where time-in-thought occurs in the comparison process. It seems, for example, that Descartes could be claiming that (i) time-in-thought is the duration of the cosmic motions themselves (i.e., a position akin to celestial reductionism), or (ii) it might be the relation determined in the act of comparing/measuring these motions against other durations (i.e., a view akin to relationalism), or it could be (iii) an idea discovered or employed when comparing these motions. Even though I have not yet established which of these options best explains time-in-thought, one can already see that any of these choices would give motions a more significant role in time-in-thought than it has for duration. Indeed, under any of these three interpretations, it seems that time-in-thought depends on motion in some way or other. Though I.57 alone does not provide sufficient grounds for ruling out interpretations (i), (ii), or (iii),[16] it does indicate that motion is somehow required for time-in-thought while it is not required for duration. Thus, I.57 does establish a significant difference between these two temporal attributes.
Recall that in Rule 12 Descartes asserts that the concepts of motion, duration, and time are such that conceiving of one somehow involves conceiving of the other(s). What was not previously determined was whether or not Rule 12 distinguishes between two different concepts by the terms ‘duration’ and ‘time.’ From I.57 we can see that ‘duration’ and ‘time’ (at least occasionally) pick out two distinct attributes. When the terms pick out duration and time-in-thought, Descartes must identify two, really distinct kinds of attributes since duration is not dependent on motion, while time-in-thought is dependent on motion in one way or another. Since one and the same thing could not be both independent from and dependent on motion, it must be the case that Descartes posits duration and time-in-thought to be numerically distinct types of attributes.
Accordingly, Principles I.57 provides a ready solution to the two, apparently contradictory ways that Descartes relates time and motion. Though it’s not clear that Descartes intends the Principles I.57’s distinction every time he uses the terms ‘duration’ and ‘time,’ when he does employ this distinction, he references two numerically distinct temporal attributes. As this numerical diversity suggests a way for him to hold that time is dependent on motion and that motion is dependent on time without thereby implying a contradiction, it seems that whenever Descartes’ relates duration, time, and motion one must consider the possibility that he is employing this distinction. By remaining mindful of this possibility, one can avoid significant interpretive puzzles, since Descartes can be understood as referencing two distinct temporal attributes, each of which bears a contrary dependence relation to motion.
Though interpreting Descartes as a temporal dualist explains the type of distinction referenced in Principles I.57, and resolves an apparent inconsistency, I don’t think that every reference Descartes makes to ‘duration’ or ‘time’ assumes this distinction. Indeed, I think that the fact that Descartes does not always reference this distinction explains why Descartes claims that ‘time’ is called the measure of movement only when it is distinguished from duration in general. Why Descartes might sometimes fail to distinguish ‘duration’ and ‘time’ seems to relate to the fact that they are both types of time (now conceived as a genus containing two types of attributes). Nonetheless, to get clear on Descartes’ account of time, one must determine if a particular usage of one of these terms is one in which Descartes is discussing the broader genus or one of the particular kinds of temporal attributes.
Descartes’ Distinct Temporal Attributes
Having established the fact of Desc
artes’ temporal dualism, I can now proceed toward the goal of explaining the distinct natures of each of the temporal attributes and how they are related. Although Descartes does not clarify whether duration or time-in-thought is more fundamental in I.57, it is duration that receives more attention in texts beyond I.57. Recall that Descartes states at the beginning of I.57 that “some attributes or modes are in the very things of which they are said to be attributes or modes, while others are only in our thought.”[17] In the sentences following, Descartes makes it clear that time-in-thought refers to the temporal attribute which exists “in thought” and that duration is the attribute “in things.” I.57’s implication that duration is an attribute inhering in things is a view that Descartes states more explicitly elsewhere. Indeed, when Descartes explains the very nature of duration in Principles I.62, he does so by indicating it to be an attribute intrinsic to substances. In I.62, Descartes explains that “a substance cannot cease to endure without also ceasing to be,”[18] and thus he claims that duration is merely conceptually distinct from substance.[19] Duration is intrinsic to the nature of substance itself because the duration of a substance is its very enduring. As duration just is the enduring of a substance, it follows that if a substance ceased to have duration then it would simply cease to be.
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