Hume's Missing Shade of Blue Re-viewed

Hume's Missing Shade of Blue Re-viewed John 0. Nelson It is obviously important for Hume's purposes in the Treatise to maintain that simple ideas are always founded in precedent, resembling impressions;1 andhe explicitly, overandover, doesso, evensometimes being so carried away by this first principle ofhis science of man (T 7) or so careless as to say that not just all simple ideas but all ideas are founded in precedent, resembling impressions. At the same time, as often noted, Hume explicitly maintains that it is possible for there to be a simple idea having no precedent, corresponding impression. He argues: There is however one contradictory phaenomenon, which may prove, that 'tis not absolutely impossible for ideas to go before their correspondent impressions ... Suppose ... a person to have enjoyed his sight for thirty years, and to have become perfectly well acquainted with colours of all kinds, excepting one particular shade of blue ... Let all the different shades of that colour, except that single one, beplac'd before him ... Now Iask, whether 'tis possible for him, from his own imagination, to supply this deficiency, and raise up to himselfthe idea ofthat particular shade, tho' it had never been conveyed to him by his senses? I believe there arefew but will be ofopinion that he can; and this may serve as a proof, that the simple ideas are not always derived from the correspondent impressions. (T 5) Nowjust prior to this concession (as Cummins calls it ), Hume has said that the full examination ofthis question [the causal relationship between ideas and impression] is the subject of the present treatise; and therefore we shall here content ourselves with establishing one general proposition, That all our simple ideas in their first appearance are deriv'd from simple impressions, which are correspondent to them, and which they exactly represent. (T 4) Volume XV Number 2 353 JOHN O. NELSON And just after the same concession, that a simple idea may be raised up which does not have a prior, correspondent impression, Hume says that it still remains true, that all our simple ideas proceed either mediately or immediately, from their correspondent impressions (T 7). Thus we have Hume explicitly asserting, it seems, both that all simple ideas have precedent correspondent impressions and that they do not. But this, on the face ofit, is an arrant contradiction! Can Hume have Homerically nodded? We have been quoting from the Treatise, but Hume makes the very same contradictory-seeming claims in the Enquiryl A thinker of Hume's acumen might nod for a page or two's quarter hour but not for all of nine years! Moreover, in both places Hume refers to the phenomenon of the impression-less idea ofblue as a contradictory phenomenon, indicating clearly enough that he was himself aware of there seeming to be an inconsistency here in his contentions. What can possibly be going on? Is Hume deliberately being paradoxical? Perhaps trying, for sensation's sake, to shock the reader and so increase sales of his work, as some commentators in the past might have wished to say? But this would be at the expense ofhis own contentions and principles and not the reader's, and not even Hume's bitterest foes and most malicious critics — so far as I know — have ever proposed that Hume would, figuratively speaking, like Oedipus, gouge out his own eyes, even in order to increase sales of the Treatise, nor does it make the slightest sense to think he would. The mystery deepens when we remember that Hume has said, in defining the program of the Treatise, that his intention is to establish the one general proposition that all our simple ideas in their first appearance are deriv'd from simple impressions, which are correspondentto them (T4). What astrange way, we want to exclaim, to show that all our simple ideas are derived from correspondent simple impressions by almost immediately afterwards arguing that it is possible to have an idea that has had no correspondent, precedent impression ! Such an egregious nonsequitur mightbe expected ofan absolutely incompetent beginner in philosophy, but we are speaking of David Hume, generally recognized as the profoundest and most acute of...