The assertion that in the vegetal and lowest animal forms of life there is an innate but unconscious intelligence, is an assertion which contains an inherent contradiction, and is therefore fundamentally irrational. Anyone who says that blind actions (in which no end is perceived or intended) are truly intelligent ones, abuses language. The meaning of words is due to convention, and anyone who calls such actions truly intelligent, divides himself from the rest of mankind by refusing to speak their language. What experience have we which can justify such a conception as that of “unconscious intelligence?” We are indeed aware of a multitude of actions which are evidently the outcome of intelligence, but which (like the analogous action of a calculating machine) are performed by creatures really unconscious, though they may possess consentience. But consciousness is the accompaniment of all those actions which we _know_ to be intellectual and rational. Our experience then contradicts the hypothesis of the existence of any such thing as “unconscious intelligence.” Such a thing is indeed no true concept, for it is incapable not only of being imagined but also of being really conceived of. It resembles such unmeaning expressions as “a square pentagon” or a “pitch-dark luminosity.” Nevertheless, our experience is _in favor_ of the existence of an intelligence which can implant in and elicit from unconscious bodies activities which are intelligent in appearance and result. Thus we can construct calculating machines and train animals to perform many actions which have a delusive semblance of rationality. “Truly intelligent action” we know as being intelligent and rational in its _foresight_, and therefore as necessarily conscious in the very principle of its being. “Unconsciously intelligent action,” improperly called “intelligent” or “wise,” is that which is intelligent and wise only as to its results, and not in the innermost principle of the creatures (whether living or mere machines) which perform such action. To speak technically, we have “formal” and “material” intelligence, as we have “formal” and “material” vice and virtue.[37] We have already distinguished between the “formal” and the merely “material” discoverer of a new fossil, and this distinction is one which it is most important to bear in mind. It is the failure to apprehend this distinction which is the root of a vast number of modern philosophical errors, and the error which consists in asserting the reality of “unconscious intelligence” is one of them. [37] Thus a man wishing to aid another, but who by miscalculation causes his death, does an action which is “materially” homicidal, though “formally” his action is a virtuous one. Similarly a man may be “materially” a bigamist but not “formally,” as when he has married a second wife being honestly convinced that his first wife was dead.