An earlier writer than Mill, John Locke (1632-1704), brings out the importance of thought for life and the need of training so that its best and not its worst possibilities will be realized, in the following words: "No man ever sets himself about anything but upon some view or other, which serves him for a reason for what he does; and whatsoever faculties he employs, the understanding with such light as it has, well or ill informed, constantly leads; and by that light, true or false, all his operative powers are directed.... Temples have their sacred images, and we see what influence they have always had over a great part of mankind. But in truth the ideas and images in men's minds are the invisible powers that constantly govern them, and to these they all, universally, pay a ready submission. It is therefore of the highest concernment that great care should be taken of the understanding, to conduct it aright in the search of knowledge and in the judgments it makes."[4] If upon thought hang all deliberate activities and the uses we make of all our other powers, Locke's assertion that it is of the highest concernment that care should be taken of its conduct is a moderate statement. While the power of thought frees us from servile subjection to instinct, appetite, and routine, it also brings with it the occasion and possibility of error and mistake. In elevating us above the brute, it opens to us the possibility of failures to which the animal, limited to instinct, cannot sink. [4] Locke, _Of the Conduct of the Understanding_, first paragraph. § 3. _Tendencies Needing Constant Regulation_ [Sidenote: Physical and social sanctions of correct thinking] Up to a certain point, the ordinary conditions of life, natural and social, provide the conditions requisite for regulating the operations of inference. The necessities of life enforce a fundamental and persistent discipline for which the most cunningly devised artifices would be ineffective substitutes. The burnt child dreads the fire; the painful consequence emphasizes the need of correct inference much more than would learned discourse on the properties of heat. Social conditions also put a premium on correct inferring in matters where action based on valid thought is socially important. These sanctions of proper thinking may affect life itself, or at least a life reasonably free from perpetual discomfort. The signs of enemies, of shelter, of food, of the main social conditions, have to be correctly apprehended. [Sidenote: The serious limitations of such sanctions]