It may be said, however, that no one, in making such a forecast, can or does rely entirely on his own experience: when endeavouring to estimate the probable effect upon his happiness of new circumstances and influences, untried rules of conduct and fashions of life, he always argues partly from the experience of others. This is, I think, generally true: but by including inferences from other men’s experience we inevitably introduce a new possibility of error; for such inference proceeds on the assumption of a similarity of nature among human beings, which is never exactly true, while we can never exactly know how much it falls short of the truth; though we have sufficient evidence of the striking differences between the feelings produced in different men by similar causes, to convince us that the assumption would in many cases be wholly misleading. On this ground Plato’s reason for claiming that the life of the Philosopher has more pleasure than that of the Sensualist is palpably inadequate. The philosopher, he argues, has tried both kinds of pleasure, sensual as well as intellectual, and prefers the delights of philosophic life; the sensualist ought therefore to trust his decision and follow his example. But who can tell that the philosopher’s constitution is not such as to render the enjoyments of the senses, in his case, comparatively feeble? while on the other hand the sensualist’s mind may not be able to attain more than a thin shadow of the philosopher’s delight. And so, generally speaking, if we are to be guided by another’s experience, we require to be convinced not only that he is generally accurate in observing, analysing, and comparing his sensations, but also that his relative susceptibility to the different kinds of pleasure and pain in question coincides with our own. If he is unpractised in introspective observation, it is possible that he may mistake even the external conditions of his own happiness; and so the communication of his experience may be altogether misleading. But however accurately he has analysed and determined the causes of his feelings, that similar causes would produce similar effects in us must always be uncertain. And the uncertainty is increased indefinitely if our adviser has to recall in memory out of a distant past some of the pleasures or pains to be compared. Thus in the ever-renewed controversy between Age and Youth, wisdom is not after all so clearly on the side of maturer counsels as it seems to be at first sight. When a youth is warned by his senior to abstain from some pleasure, on the ground of prudence, because it is not worth the possible pleasures that must be sacrificed for it and the future pains that it will entail; it is difficult for him to know how far the elder man can recall--even if he could once feel--the full rapture of the delight that he is asking the younger to renounce.