FOOD, SHELTER, AND SEX. Thus far our analysis has been confined to the general types of human behavior. We have found that all human activity is conditioned by a native equipment consisting of certain more or less specific tendencies to action, and that these may be modified into acquired tendencies called "habits." We have found that through the processes of reflection, through imaginative trial and error, both of these may, within limits, be controlled. We must now proceed to an inventory of those elements of our native equipment which have an especial significance in social life. In the first place, we must note the three great primary drives of human action, the unlearned and native demands for food, shelter, and sex gratification.[1] Although the last-named does not display itself in human beings until a considerable degree of maturity has been attained there is indubitable evidence that it is an inborn and not an acquired reaction. The practical utility of the first two is apparent; they are the most essential features of the group of so-called self-preservative instincts, among which may be grouped the natural tendency to recover one's equilibrium and the instinct of flight in the face of dangerous or threatening objects. The utility of the sex instinct is racial rather than individual. The instinctive satisfaction human beings find in sex gratification is the natural guarantee of the continuance of the race. [Footnote 1: The reader must be reminded that the simpler reflexes involved in the use of the heart, lungs, intestines, and all the internal organs, must be classed as part of man's native equipment. They differ from those reactions commonly classed as instincts in that they are simpler and stabler, that in their normal functioning they never rise to consciousness, and that they are almost completely beyond the individual's modification or control.] In a general survey of this nature it IS impossible, as it is unnecessary, to examine in detail the physiological elements of the demand for food and shelter. It will suffice to point out that the first two are the ultimate biological bases of a large proportion of our economic activities. They are primary, not in the sense that they are constantly conscious motives to action, but that their fulfillment is prerequisite to the continuance of any of the other activities of the organism. Agriculture and manufacture, the complicated systems of credit and exchange which human beings have devised, are, for the most part, contrivances for the fulfillment of these fundamental demands. With the complexity of civilization new demands, of course, arise, but these fundamental necessities are still the ultimate mainsprings of economic production.