Doubt, if you can, everything. This Descartes attempted, and he claims to have not only successfully doubted all, but moreover to have returned from the void, the foundations of his beliefs being thereby rendered unquestionable. But I cannot go so far; there is much that I cannot doubt. Descartes claims that in his doubt of all, he could nonetheless prove his own existence, for “Cogito, ergo sum.” But I ask, whence “therefore”? How does he who doubts everything know that what thinks exists? For my part, I need no such argument, for I am simply unable to doubt my own existence. Imagine that you do not exist, not by imagining a world in which you had not been born, or a time in this world before you had been born, but thinking that here, now, you do not exist. For my part, I cannot; my power of doubt fails me.
Thus I have a piece of knowledge. But of what nature is it? It is not objectively certain, I suppose; I have not derived it by infallible syllogism from objectively certain premises. But if it is uncertain from this objective standpoint, it is nonetheless subjectively certain,1 for I cannot think otherwise. And if, come what may, I shall never doubt it, what matters the method of its proof? And what, indeed, would an objective proof be? The result of a deduction? But whence the premises? Whence the rules of inference? Objective proof is only possible within a framework to provide premises and a logic. Objective proof of such a framework is impossible.
Consider the principles of propositional logic. ‘A or not A’, and certainly not both. How do we know this? Not from any logic, for it is logic that we seek to prove. Rather, my grounds for belief in the principles of logic are the same as for my belief in my own existence. Without sophistry, attempt to believe both that it is and that it is not snowing. I simply do not know what that would mean. Just as I cannot doubt that I exist, I cannot believe that a contradiction is true. Or believe that it is neither snowing nor not snowing. Again, my powers of mind fail me, and I cannot. Or believe ‘If A then B, but A and not B’. Again, the statement is meaningless to me. Although I cannot prove it false, neither can I doubt its falsity.
Thus I may more clearly state the relationship between subjective and objective proof. An objective proof is interpersonally valid, but hypothetical, so that while those who accept the framework assumed are bound on pain of inconsistency to accept the conclusion, those who deny its foundations are bound to nothing. Subjective proof, by contrast, is not interpersonally valid; indeed, the proof is intrinsically incommunicable, being the inability to doubt the proposition proved. However, while objective proof binds conditionally, subjective proof binds absolutely: one who professes disbelief in what he cannot doubt denies himself. Thus we may define reason as consistency, but in two forms. One is objectively rational if he accepts all that his beliefs bind him to accept, and deny all that they bind him to reject (as a corollary, to be objectively rational one’s premises must be consistent, for otherwise those two tasks would be jointly impossible). One is subjectively rational if one’s intentional beliefs are consistent with one’s deeper beliefs.2
Thus far I have dealt with propositions. But there is one more element in the wall that prevents me from following Descartes into the void of total doubt, one question that refuses to pass unanswered: what ought I to do? The question is uniquely persistent in that any attempt to ignore it is itself an answer (“I ought not to answer that question”, or some more complex variation). Nor can I answer with mere opinion, for that too is a factual answer (“I ought to do as I please”). Fortunately, to this normative question correspond normative subjective facts. I ought to seek the truth, not falsehood; I could never consciously believe what I thought false.3 Similarly, I cannot doubt that good is to be pursued, and evil avoided, above all other considerations. These answers, a deduction of which has tormented the positivists, who sought proof in science, come easily unto me, for unlike scientific proof, subjective proof cares little whether a proposition is normative.
1: This essay does, I admit, attempt to prove the subjectivity of truth. But subjectivity must not mean relativism; I assert that there are no grounds for belief apart from the individual mind (for how could there be any which are not perceived through that mind?), but not that the truth thereby found will be different for different minds, and emphatically not that we can choose what is true.
2: I see the power of this definition in analysis of the self-proclaimed relativists who nevertheless tend to be rather dogmatic about their relativism. Their profession of relativism clashes with the fact that one cannot truly doubt that some things simply are true, and this deeper belief in the existence of interpersonal truth clashes with their professed belief to create the wildly inconsistent statements that one occasionally sees, in which self-proclaimed relativists assert the absolute truth of relativism, or some other branch of political correctness.
3: This is not to say that people cannot have subconscious impulses toward believing what is false (on which see Bryan Caplan’s work on rational irrationality), but merely that one could never consciously do so without badly twisting definitions.