If a man always acts for his greatest present pleasure, real and imaginary, it seems a far step to say that he "ought" to act--or in any way to expect that he will act--at each moment for the greatest sum of pleasure attainable in the probable duration of his life. But on reflection, this may turn out to follow if we postulate that conduct can be rationalised. What is meant by this egoistic "ought" may be said to be simply that to the eye of reason the pleasure of any one moment cannot be regarded as more valuable than the equal pleasure of any other moment, if it is equally certain; and that therefore to act as if it were is to act unreasonably. Man fails in acting up to reason in this sense, because his action is not motived by reason, but directly by pleasure and pain; and not by a mere estimate of pleasure and pain, but by pleasure and pain themselves. The psychological hedonist must maintain that the estimates of future pleasure and pain only become motives by being not merely recognised (intellectually) but felt (emotionally)--that is, by themselves becoming pleasurable or painful. If the Egoist calls any action irrational, it cannot be because the motive which produced it was not the greatest pleasure in consciousness at the time. It can only be on the ground that the greatest pleasure in consciousness at the time is likely to lead to a sacrifice of greater pleasure in the future; and this must be due either to intellectual misapprehension or to the imagined fruition of future pleasure not being strong enough to outweigh the pleasure which comes from a present stimulus, and to the imagined fruition of the more distant being weaker than that of the less distant pleasure. It is owing to a defect of the imagination on a man's part that even with complete information he does not act "up to his lights"--irrational action being partly a consequence of insufficient acquaintance with the normal results of conduct, partly due to defective imagination. Were a man's imagination of future pleasure and pain as strong as his experience of present pleasure and pain, and did he correctly appreciate the results of his conduct, then his action would, of psychological necessity, harmonise with the precepts of egoistic hedonism. [Sidenote: the latter of which] [Sidenote: is inconsistent with the nature of voluntary action.]