e.g., “I feel cold”. For in most cases in which such a statement is made it would not be true to say “I cannot conceive myself not feeling cold,” since only very intense sensation excludes the imagination or conception of a feeling opposite in quality. We might, no doubt, say “I cannot conceive that I am not feeling cold”: but the form of this sentence shows that I have passed from conception, strictly taken, to belief. Spencer’s contention that in this case the connexion of the predicate-notion “feeling cold” with the subject-notion “self” is for the time “absolute,” though only “temporarily,” seems to me to ignore the complexity of consciousness. According to my experience, disagreeable sensations, when not too violent, even tend to excite the opposite imagination: e.g., great thirst is apt be attended by a recurrent imagination of cool spring water gurgling down my throat. I cannot therefore agree that the utmost certainty in a proposition representing a transient empirical fact involves the “inconceivability” of its negation—except in a peculiar sense of the term in which it is equivalent to “intuitive incredibility”.
It is no doubt otherwise in the case of universal propositions intuitively known—or, in Mr. Spencer’s phrase, “cognitions in which the union of subject and predicate is permanently absolute”. I cannot imagine or conceive two straight lines enclosing a space: here “intuitive incredibility” coincides with “inconceivability” in the strict sense; only either attribute must be taken with the qualification that I can suppose my inability to conceive or believe to be due to a defect of my intellect.
With this explanation, I shall allow myself to use Mr. Spencer’s term in a stricter or looser sense, according as the cognition in question is universal or particular. I have no doubt that “inconceivability of negation,” so understood, is normally an attribute of propositions that appear self-evident truths; I think that, in trying to apprehend distinctly the degree of certainty attaching to any such proposition, we commonly do apply—more or less consciously—Mr. Spencer’s test, and that a systematic application of it is a useful protection against error. But I think that the objection before urged against the infallibility of the Cartesian criterion applies equally to Mr. Spencer’s. Indeed he admits “that some propositions have been wrongly accepted as true, because their negations were supposed inconceivable when they were not”. But he argues that this “does not disprove the validity of the test”; chiefly because (1) “they were complex propositions, not to be established by a test applicable only
