For ‘tis evident, that if a person full-grown, and of the same nature with ourselves, were on a sudden transported into our world, he wou’d be very much embarrass’d with every object, and would not readily find what degree of love or hatred, pride or humility, or any other passion he ought to attribute to it. The passions are often vary’d by very inconsiderable principles; and these do not always play with a perfect regularity, especially on the first trial. But as custom and practice have brought to light all these principles, and have settled the just value of every thing; this must certainly contribute to the easy production of the passions, and guide us, by means of general establish’d maxims, in the proportions we ought to observe in preferring one object to another. (Hume Treatise 2.1.6)
Suppose a person, though endowed with the strongest faculties of reason and reflection, to be brought on a sudden into this world; he would, indeed, immediately observe a continual succession of objects, and one event following another, but he would not be able to discover any thing farther. He would not, at first, by any reasoning, be able to reach the idea of cause and effect; since the particular powers, by which all natural operations are performed, never appear to the senses; nor is it reasonable to conclude, merely because one event, in one instance, precedes another, that therefore the one is the cause, the other the effect. Their conjunction may be arbitrary and casual. There may be no reason to infer the existence of one from the appearance of the other. And in a word, such a person, without more experience, could never employ his conjecture or reasoning concerning any matter of fact, or be assured of any thing beyond what was immediately present to his memory and senses.--David Hume Enquiry Concerning Human Understanding, 5.3).
Could we conceive a person of the soundest judgment, who had grown up to maturity, and whose imagination had acquired those habits, and that mold, which the constitution of things in this world necessarily impress upon it, to be all at once transported alive to some other planet, where nature was governed by laws quite different from those which take place here; as he would be continually obliged to attend to events, which must to him appear in the highest degree jarring, irregular, and discordant, he would soon feel the same confusion and giddiness begin to come upon him, which would at last end in the same manner, in lunacy and distraction. Neither, to produce this effect, is it necessary that the objects should be either great or interesting, or even uncommon, in themselves.--Adam Smith, "The History of Astronomy."
Jeff Bell has returned to regular blogging! (Hurray!) Recently he wrote a wonderful series of posts on Hume, Spinoza, and Deleuze in which he called attention to the two passages from Hume quoted above. One striking claim in the passage from the Treatise that Bell does not remark upon is Hume's claim that "custom and practice...have settled the just value of every thing." (Hume repeats the claim with the same thought experiment in his dissertation on the passions.) It is tempting to see in this some kind of long run equilibrium claim. Even so, one doesn't need to know Hume's account of taste (combined judgments of true judges set value), his account of economics (value is established in the market), or his mistrust of theodicy, to find this is a bit surprising. For at the very start of the Treatise, Hume had bemoaned that metaphysics was being unfairly undervalued (despite there being "just value for every other part of literature") by the learned! So, Hume knows that custom and practice cannot be expected to produce just values in philosophy.