Clarification of the Descartes/Hume/Kant Axis
§1: a classic argument in the history of psychophilosophy
it is commonly thought that Descartes failed to adequately distinguish the I2 and the I3; and, my translation of Descartes' cogito into HE has an extended discussion of this point.
this failure contributed to the suggestion that the phenomenon of self-awareness (I2 am aware of I2) was also awareness of self (I2 am aware of I3). Hume objected to this:
There are some philosophers who imagine we are every moment intimately conscious of what we call our SELF; that we feel its existence and its continuance in existence; and are certain, beyond the evidence of a demonstration, both of its perfect identity and simplicity. ...
Unluckily all these positive assertions are contrary to that very experience, which is pleaded for them, nor have we any idea of self, after the manner it is here explained. For from what impression could this idea be derived? This question it is impossible to answer without a manifest contradiction and absurdity; and yet it is a question, which must necessarily be answered, if we would have the idea of self pass for clear and intelligible, It must be some one impression, that gives rise to every real idea. But self or person is not any one impression, but that to which our several impressions and ideas are supposed to have a reference. If any impression gives rise to the idea of self, that impression must continue invariably the same, through the whole course of our lives; since self is supposed to exist after that manner. But there is no impression constant and invariable. Pain and pleasure, grief and joy, passions and sensations succeed each other, and never all exist at the same time. It cannot, therefore, be from any of these impressions, or from any other, that the idea of self is derived; and consequently there is no such idea.
thus, Hume's first argument is: I2 can not find the source of the idea of the I3; therefore, there is no I3.
... what must become of all our particular perceptions upon this hypothesis? All these are different, and distinguishable, and separable from each other, and may be separately considered, and may exist separately, ... . After what manner, therefore, do they belong to self; and how are they connected with it? For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception. When my perceptions are removed for any time, as by sound sleep; so long am I insensible of myself, and may truly be said not to exist. ...
I may venture to affirm of the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement. Our eyes cannot turn in their sockets without varying our perceptions. Our thought is still more variable than our sight; and all our other senses and faculties contribute to this change; nor is there any single power of the soul, which remains unalterably the same, perhaps for one moment. The mind is a kind of theatre, where several perceptions successively make their appearance; pass, re-pass, glide away, and mingle in an infinite variety of postures and situations. There is properly no simplicity in it at one time, nor identity in different; whatever natural propension we may have to imagine that simplicity and identity. The comparison of the theatre must not mislead us. They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place, where these scenes are represented, or of the materials, of which it is composed.
Hume, David. Treatise of Human Nature. Book I, Part IV, §6: Of Personal Identity. online edition.
Hume's second argument seems to be: I2 may notice that I2 am experiencing heat, cold, light, pain or whatever; but I2 never observe I3; therefore, there is no I3 and, furthermore, there is no I2 either.
there may be some ambiguity in Hume's claim in that it is not entirely clear whether he expected to observe I2 or I3; but, it is clear that he didn't make the expected observation and, in what appears to be a distortion of the scientific method, denied the reality of both I2 and I3 as a consequence.
if the hypothesis that Hume was 'testing' was that the I2 might observe the I3 by means of the procedure he used (noticing the thoughts, feelings and sensations that the I2 experienced); then, having failed to make the predicted observation, he entitled to conclude that the I2 could not observe the I3 (if any) in this manner. concluding that neither the I2 nor the I3 were real seems like overkill.
however, we might also ask why such overkill seemed plausible to Hume; and, one possible explanation is that he made the same mistake that Descartes made: conflating the I2 and the I3. if Hume was 'testing' that claim of identity; then, he would have been entitled to reject it when he called his experiment to a close and reported negative results.
in any event, Hume earned his place in the history of psychophilosophy as the I2 that proved to its own satisfaction that it was unreal but self-aware.
some years later, Kant came along and provided some balance to Hume's extreme methods. consider this passage from Kant's Critique of Pure Reason:
... so far as I think myself, it is really impossible by that simple self-consciousness to determine the manner in which I exist, whether as a substance or as an accident. Thus, if materialism was inadequate to explain my existence, spiritualism is equally insufficient for that purpose, and the conclusion is, that, in no way whatsoever can we know anything of the nature of our soul, so far as the possibility of its separate existence is concerned.1
I2 would translate this into HE thus:
I2 am aware of I2; but, from simple I2-awareness it is impossible to determine the reality type of Ix (the separate reality from which I2 originate). Thus, materialism is insufficient for this purpose (because it assumes that Ix = I1); and, spiritualism is equally insufficient for this purpose (because it assumes that Ix = I3). Thus, I2 conclude that there is no way (thru use of logic/reason, anyway) to prove any conclusion about the reality type of the Ix.
the clear implication is that one knows that the Ix is real; but, not what its reality type is.
thus, we have come full circle; having returned to that moment in Descartes' Second Meditation where he knows that I2 am; but, not what Ix am.