A technician explains measurements whilst a scientist explains observations.

You are totally incorrigible

"I have time-extended images therefore I am."

Descartes said "cogito ergo sum", "I think therefore I am". This simple statement is regarded by many as the definite truth on which philosophy might be based. (See Note 2).

Over the years, people have become confused about what "cogito ergo sum" actually means. Nowadays people use the word "think" to mean inner speech but in Descartes' time philosophers used it to mean mental images, sensations, perceptions, inner speech, feelings etc. so "cogito ergo sum" meant "I am a mind" or more simply "stuff happens"! (see Note 2) You cant argue with that, its an incorrigible argument.

Descartes courtesy Wiki Commons

The misunderstanding about the nature of 'think' in the 'cogito' has also confused people about the geometrical nature of Descartes' statement. Descartes' "think" included phenomena such as mental images and the statement "There are images therefore I am" leads the scientist to a different analysis from "There is inner speech therefore I am".

Another way in which people have misunderstood the "cogito" is that they have ignored Descartes' description of things happening for whole durations of time. Descartes' thoughts are time extended images so the 'cogito' is truly "I have time extended images therefore I am". As an example of this misunderstanding, Daniel Dennett in his book "Consciousness Explained" and in his article "Quining Qualia", assumes that only the present instant exists so that the mind has no duration. It is then simple to argue that the mind cannot know itself because at any moment it would misremember or misjudge what went before. So, according to Dennett stuff happens but we've got no idea about whether it really happened or not. (See Note 1 below).

There is a self contradiction in Dennett's argument because if time does not exist and the present has no duration (being zero seconds long) then nothing could be known because we would have no time to know it. Dennett could not even know his own argument.

Dennett should be forgiven for this argument because he is using widely accepted school book cosmology, in which time is a simple succession of three dimensional instants, to argue away his mind. Dennett's real message is to show how cosmological ideas can undermine our belief in everyday reality (See Presentism and the Denial of Mind). If you have erroneous ideas about how space, time and matter are interrelated then you will have all sorts of dubious ideas. The empirical truth is that we obviously do have minds and our minds extend over a whole interval of time so that we can be aware at any moment (See Time and conscious experience). Explaining this experience will require more advanced cosmological ideas than the "folk physics" used by Dennett.

Perhaps a modern statement of incorrigibility is needed. If there is a continuous event in my experience, whether in perception or in a dream, then it is present now. Existing events are events that are present now. If an event is present now there is no time for further processing or change of the event between now and when it is occurring. So present experience is incorrigible.


Note 1: Dennett (1988) says:
"The infallibilist line on qualia treats them as properties of one's experience one cannot in principle misdiscover, and this is a mysterious doctrine (at least as mysterious as papal infal libility) unless we shift the emphasis a little and treat qualia as logical constructs out of subjects' qualia-judgments: a subject's experience has the quale F if and only if the subject judges his experience to have quale F."

Notice how he redefines experience as a judgement of experience. Once he has done this Dennett can use school cosmology to deny it.

Note 2: Descartes' 'cogito' was stated by him as:

"But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search."

Descartes is clear that what he means by thought is all the things that occur in experience, whether dreams, sensations, symbols etc.:

"5. Of my thoughts some are, as it were, images of things, and to these alone properly belongs the name IDEA; as when I think [ represent to my mind ] a man, a chimera, the sky, an angel or God. Others, again, have certain other forms; as when I will, fear, affirm, or deny, I always, indeed, apprehend something as the object of my thought, but I also embrace in thought something more than the representation of the object; and of this class of thoughts some are called volitions or affections, and others judgments." (Meditation III).


Daniel C Dennett. (1988). Quining Qualia. in A. Marcel and E. Bisiach, eds, Consciousness in Modern Science, Oxford University Press 1988. Reprinted in W. Lycan, ed., Mind and Cognition: A Reader, MIT Press, 1990, A. Goldman, ed. Readings in Philosophy and Cognitive Science, MIT Press, 1993. http://ase.tufts.edu/cogstud/papers/quinqual.htm

Dennett, D. and Kinsbourne, M. (1992) Time and the Observer: the Where and When of Consciousness in the Brain. (1992) Behavioral and Brain Sciences, 15, 183-247, 1992. Reprinted in The Philosopher's Annual, Grim, Mar and Williams, eds., vol. XV-1992, 1994, pp. 23-68; Noel Sheehy and Tony Chapman, eds., Cognitive Science, Vol. I, Elgar, 1995, pp.210-274.http://ase.tufts.edu/cogstud/papers/time&obs.htm


  1. John, if presentism is mistaken as an understanding of time, then I take it that you suppose something like the block universe view of spacetime is the case: that all moments, past, present and future equally exist. Just wondering if I'm correct in this assumption, and if so you might enjoy "Scripting the future: spacetime and the nature of control," http://www.naturalism.org/spacetime.htm Or you might have corrections to offer.


    Tom Clark

  2. Hi Tom, thanks for the comment. I like the endnotes in your article which emphasise that there is still much to be known about space and time. My empirical observation is that my own past is fixed and my experience contains a segment of this fixed past. As for the future, it is not within my experience at any moment so I have no personal observational inspiration beyond the fact of 'becoming'. Becoming is strange because as McTaggart spotted, we can only appear to move through dimensional time if we are not fixed within dimensional time. Putting these two types of temporal experience together (dimensional time and change/becoming) my hunch is that the future is open because we are moving outside of any block universe.

    We could be outside of a block universe if there were a fifth extensive, time-like dimension or if spacetime is actually generated by QM phenomena - or for some other reason that is presently unsuspected.

  3. Thanks John. I'm not sure that "we can only appear to move through dimensional time if we are not fixed within dimensional time," since such an appearance might be generated in some other way that doesn't put us outside the block universe. We can of course speculate about what physical theory might come up with, but my approach is just to follow what looks to be the current consensus among physicists about spacetime.

  4. TC: "but my approach is just to follow what looks to be the current consensus among physicists about spacetime."

    That is also my approach. What do you think is the current consensus? I think the current majority view amongst theoretical physicists, that space-time is probably selected or separated from an infinite dimensional Hilbert space at each instant, answers McTaggart's problem. However I am also open to other ideas.

  5. Exactly how much consensus exists within the physics community on the block universe view isn’t clear (shall we do a poll? :-). Physicist Brian Greene seems to suggest that it is the consensus when he says: “Time is a subtle subject and we are far from understanding it fully. It is possible that some insightful person will one day devise a new way of looking at time and reveal a bona fide physical foundation for a time that flows.” (p. 141, The Fabric of the Cosmos) I also asked Sean Carroll at Cosmic Variance about it, and his opinion was the block universe view was the majority position (personal correspondence). But of course this could change, so like you I remain open to other ideas.

  6. I agree with your quote: "some insightful person will one day devise a new way of looking at time and reveal a bona fide physical foundation for a time that flows". This apparent flow of events is the most extreme problem with our idea of time.

    I agree with Carroll, there seems little doubt to me that the dimensional time in Relativity Theory exists but this does not account for a "time that flows". This suggests that what we call "time" is a mixture of correlated phenomena. The statement "a time that flows" conjures up a "rate of time" and is actually an implied postulate of a fifth, time-like dimension - Alex Green suggested that there was was a positive time-like dimension (see Alex Green's Original Paper) on the basis of our empirical experience but I am uneasy about such a drastic modification to cosmological theory without a set of predictions for how this would affect particle theory etc.

  7. Hi John
    I'm just an amateur Thomist with a lifelong interest in ... what can one say.. reality. I find your website a marvelous, provocative and challenging education. That said, I read Norris Clarke's "The One and the Many" in the course of which reading, I became pretty convinced that our Newtonian notions of ontologically real things called "space and time" refer to things that exist formally, but not materially. Between you and Montreal is not space filled with trucks and roads and farms and rhombi, but just the roads and farms and trucks. Time Clarke describes as a function of sense memory and anticipation. There is nothing that "flows" etc. Things are materially related and in act. Thanks