Skepticism and Time

Skepticism and Time

We can’t be certain the ordinary world of material objects exists: we might be brains in a vat or perpetually dreaming. We can’t be certain that space exists, at least in the form we think of it, for the same reasons. But what about time? We are familiar with skepticism with respect to the contents of time: the world might have been created ten minutes ago and have a very different history from the one we suppose. But might the past not exist at all? Might the future be a figment? What about the present—does it too fall to the skeptic? In the case of the present things look more hopeful: we can know for certain that it exists. How? By a version of the Cogito: if I am thinking now, then there must be a now for me to think in. Every occurrence needs a time in which to exist. Nothing happens without a time in which it happens. Even if I am only dreaming, my dream needs a time to occur in. Thus, we can confidently assert: “I think, therefore the present time exists”. There is no epistemically possible world in which I am thinking but there is no time. What the nature of this time is we may not know, but we know at least that the present moment is real: an existent thing falls under the concept the present, viz. a certain temporal moment. But the Cogito by itself doesn’t take us any further into time: maybe the present time exists but not past or future times. These are distinct existences, after all.

However, on reflection we can deduce the past and the future from the present: for what is present will soon be past and was once future. There can be no present without a past and future. It is a necessary a priori truth that a present moment exists within a series of moments some of which are in the past and some in the future. This follows from the fact that time flows, i.e., moments pass from future to present to past. No moment can be stuck in the present, incapable of becoming past and never having existed in the future. Every moment of your life was once a future moment and will become a past moment—as sure as eggs are eggs (a plain tautology). So, the present contains the seeds of the past and the future: at the moment you think “I think” that moment quickly moves into the past and was once a future moment. Thus, if we combine the temporal Cogito with this logico-metaphysical fact about time, we can deduce the result that past times and future times indubitably exist. What happens in or at these times is not certain, but that they exist (those times) is certain. Time might itself be relative or absolute, a matter of mechanical clocks or of God’s eternal mind, discrete or continuous, infinite or finite—but at least we know that it exists. Time logically follows from consciousness: the one kind of existence leads inexorably to the other. This is something. Matter doesn’t follow, space doesn’t follow, numbers don’t follow: but time does.[1] Time is one of life’s great certainties. Odd that Descartes didn’t make more use of this truth. We don’t need God’s assistance to know that time exists; it is built into the very nature of experience. I can never say, “For all I know, time doesn’t exist”.

[1] We might be able to get from consciousness to matter, space, and even numbers by constructing clever philosophical arguments, but in the case of time we don’t need such ingenuity—time is written right into consciousness as a surface feature. Not the impression of time, mark, but time itself.

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11 replies
  1. Free Logic
    Free Logic says:

    I am probably missing something, but would you mind elaborating on how is “Every moment of your life was once a future moment” as certain as “eggs are eggs”? How are these two even comparable? The latter is a tautology whereas the former is an assumptions in metaphysics. What is an argument against the denial of it? One does not have to be a skeptic to hold that every moment of your life did not exist at all until it actually came about?

    Reply
    • Colin McGinn
      Colin McGinn says:

      Alike in both being obvious a priori truths (I’m using a bit of hyperbole). Do you think “Everything is self-identical” is just an “assumption of metaphysics”? Isn’t it simply self-evident? Every future moment exists (tenselessly); of course, it doesn’t now exist (tensed). Also, I mean the stretch of time not what happens at that time.

      Reply
      • Free Logic
        Free Logic says:

        “Everything is self-identical” is self-evident as long as we ignore the element of time in evaluating this statement. I mean if we don’t ask whether Bob the aging politician is self-identical to Bob the young football player he was once. But “Every moment of your life was once a future moment” is not self-evident as the element of time can’t be ignored in evaluating its truth value.

        FWIW — under your influence having read and admired Logical Properties a long time ago — I think I understood what you called “your realist anti-naturalism about logical properties. But there you were talking about identity, existence, predication, necessity and truth whereas here I believe you extend this very attitude to space, time, matter and mind. My point is that these 9 fundamental concepts are so closely related and impact the resulting overall philosophical conception so strongly that it would be worth elaborating on that more explicitly. If I got this wrong — apologies for wasting your time.

        Reply
        • Colin McGinn
          Colin McGinn says:

          There are clearly properties of time that are self-evident and a priori: that time has no end, that it is composed of parts, that it has a direction, that it is measurable, that it has no color, that nothing can be past and present at the same moment, etc.

          Reply
  2. Giulio Katis
    Giulio Katis says:

    I think a statement like “the experience of instantaneous variation or immediate change in state is just as indubitable as, perhaps more real than, the experience of a single state” is compelling. But does the concept of Time you are using in this post contain more than an immediate change in state (where the change is itself conceived of as the present)? If so, at what point does memory enter the story? At some point my memories could be fabrication. But what about my short term memories, including the words that started the sentence I may be mid-way through uttering? I feel it is difficult to have a fruitful discussion on this topic without some discussion of the concept of “state” that includes some notion of complex or compound state. Maybe concepts from music may be helpful.

    Reply
    • Colin McGinn
      Colin McGinn says:

      There are many views of the nature of time, among them those that treat the passage of time as a change of state. I don’t subscribe to such views, since I believe in time without change; but I don’t want to presuppose this type of view in the post. Time is a very difficult topic.

      Reply
  3. Giulio Katis
    Giulio Katis says:

    Let’s put aside the question of state. Thought in general must involve more than a series of discrete isolated unconnected “atomic” thoughts. For instance, we often think in terms of sentences. As an analogy we may think of an extended or compound thought (as expressed in a sentence, such as “cogito, ergo sum”) as a string of beads. Is the Time you write of in this post that which lets us/our minds thread individual thoughts into a compound thought? If so, then I agree this Time seems to be more than a product of the mind (like a concept such as space), but rather some fundamental part, capacity or expression of it.

    Reply
    • Colin McGinn
      Colin McGinn says:

      I don’t think time is mental at all. It exists independently of the mind. The same is true of space and matter. We must not confuse what time is with how we know about or apprehend it.

      Reply
      • Giulio Katis
        Giulio Katis says:

        A [tree] is not mental, but our conception of it is. The comment I was making about time pertained to the nature of mind, or the thinking aspect of mind at least. It Is temporal (which I assumed was your point, but perhaps I misunderstood). But the additional point I am making is that the temporal nature is not just that of merely a succession, but also involves structure in some sense (enables the content of a “sentence” of thought, for example). I haven’t previously considered this connection between time and structure.

        Reply
        • Colin McGinn
          Colin McGinn says:

          Clearly, consciousness exists in time, as does the weather. Clearly, too, thoughts are structured entities occurring in time, as is digestion or respiration. All events are temporal and many events (perhaps all) are structured, e.g. utterances and reproduction.

          Reply
          • Giulio Katis
            Giulio Katis says:

            I may be using the word structure in a different way. I was referring to the relationship between time and atemporal structures (that are geometric-combinatorial or have information bearing capacity). Time permits the creation of such structures via (not necessarily psychological) “memory” formation; and behaviours or “stories” can be read out or unraveled from such structures in time (perhaps this only happens in the context of biological or cultural processes). Though this is obvious, that and how it happens isn’t (to me at least). And is this just an accident, or does it reflect something deep about time?

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