The chief difficulty of the theory of bodily advantage and disadvantage as conditioning pleasure and pain comes not from any such instance as the sugar of lead phenomenon; but it lies in the fact that life progressiveness, enlargement, specialization, that which is to the highest profit of life, is uniformly reached only by painful struggle. It is only by intense struggle, by supremest, painfullest effort, that those new psychic forms are initiated and developed which are of the utmost service to the organism. The act of adjustment to a new circumstance is so extremely difficult and painful that it is attempted by few and achieved by very few of any set of organisms. By an act of most painful struggle the fittest survive; and the rest, the vast majority, who could not key themselves to that pitch, perish. Adjustment to the ordinary conditions is simply a free using of intelligence and energy integrated and stored by ancestors when these conditions were new to them. The adjustments which are so spontaneously made by new-born animals as response to environment were once new, and secured and integrated for inheritance by the most painful and persistent effort. Such is the inertia and conservatism of life that while it moves spontaneously in grooves already made, it does not rejoice in the toil of real progress. The struggle by which the greatest life advances have been accomplished has always been intensely painful in itself, whatever the aftermath of pleasure may be, the pleasure of achievement and creation, the satisfaction at successful effort, which is plainly a very late psychosis.