In order to do anything intelligently a certain degree of reflection is necessary. This is particularly obvious with regard to any practical activity or occupation. Take, for example, the case of a naїve bricklayer. Let us assume that this man never reflects upon the nature of his occupation, but simply looks upon it as a more or less mechanical procedure of laying one brick upon another for a certain period of time during the day. He does not relate his occupation with the occupations of his fellow–workmen, or even with the purpose of erecting buildings. If such a man were left to his own devices on a desert island with a plentiful supply of bricks and mortar, we could imagine him erecting a gigantic pinnacle of bricks, without purpose or meaning, where a more intelligent man would have endeavoured to construct a shelter against the rigours of the climate.