The chief perplexity, however, which besets this subject and makes discussions of it so often end in a cloud, is quite artificial. Thought is not a mechanical calculus, where the elements and the method exhaust the fact. Thought is a form of life, and should be conceived on the analogy of nutrition, generation, and art. Reason, as Hume said with profound truth, is an unintelligible instinct. It could not be otherwise if reason is to remain something transitive and existential; for transition is unintelligible, and yet is the deepest characteristic of existence. Philosophers, however, having perceived that the function of thought is to fix static terms and reveal eternal relations, have inadvertently transferred to the living act what is true only of its ideal object; and they have expected to find in the process, treated psychologically, that luminous deductive clearness which belongs to the ideal world it tends to reveal. The intelligible, however, lies at the periphery of experience, the surd at its core; and intelligence is but one centrifugal ray darting from the slime to the stars. Thought must execute a metamorphosis; and while this is of course mysterious, it is one of those familiar mysteries, like motion and will, which are more natural than dialectical lucidity itself; for dialectic grows cogent by fulfilling intent, but intent or meaning is itself vital and inexplicable. [Sidenote: Perception cumulative and synthetic] The process of counting is perhaps as simple an instance as can be found of a mental operation on sensible data. The clock, let us say, strikes two: if the sensorium were perfectly elastic and after receiving the first blow reverted exactly to its previous state, retaining absolutely no trace of that momentary oscillation and no altered habit, then it is certain that a sense for number or a faculty of counting could never arise. The second stroke would be responded to with the same reaction which had met the first. There would be no summation of effects, no complication. However numerous the successive impressions might come to be, each would remain fresh and pure, the last being identical in character with the first. One, one, one, would be the monotonous response for ever. Just so generations of ephemeral insects that succeeded one another without transmitting experience might repeat the same round of impressions—an everlasting progression without a shadow of progress. Such, too, is the idiot’s life: his liquid brain transmits every impulse without resistance and retains the record of no impression.