There is another problem with Hume's account of belief, one he nowhere addresses and of which he may perhaps even not have been aware. We do not believe ideas, lively or otherwise. We believe propositions. We do not believe something; we believe that something. Interestingly, the French language, with which Hume was of course completely conversant, draws this distinction quite clearly by means of the verbs savoir and connaître. "Savoir" is used when we wish to say that we know that something is the case, or that we know some fact. "Do you know that Paris is the capital of France? Yes, I know it. Oui, je le sais." But, "Do you know Paris?" [meaning, are you acquainted with Paris, have you ever been there?] "Yes, I know Paris. Oui, je le connais." Hume's simple copy theory of ideas seems not to make a place for propositional knowledge, or for our beliefs in propositional assertions. I have no idea, quite frankly, how Hume might have accommodated such assertions in his psychological account of belief.
To sum up Hume's account of our [rationally unwarranted] belief in causal inference: Experience presents us with a never-ending flow of impressions, in which we discern certain patterns -- repeated conjoinings in space and time of resembling instances. [Resemblance, let us recall, is on Hume's view a brute fact of our experience neither requiring nor having any further explanation.] These constant conjunctions trigger in us a propensity, which we bring to experience, to form habits of association. After several repetitions of such conjunctions, we come to expect the second of a pair of impressions when we are presented with the first. If the second impression is not forthcoming, we form the idea of it, which is to say a copy of one of the previously perceived instances. Furthermore, the habit we have thus formed conveys to the idea a certain amount of the force and vivacity possessed by the present impression, and the idea, thus enlivened, is believed [to exist, is what is presumably elided here]. We conceive the pair as necessarily connected, and the idea of this necessity is actually the idea of the habit or disposition thus formed and triggered. Because the propensity to form such dispositions or habits of association is one of the "permanent, irresistible and universal" propensities of the mind, without which "human nature must immediately perish and go to ruin," we neither should nor could suspend its operations. Indeed, it is all we can do for a few hours to even contemplate its abrogation. But nature can be counted on to reassert itself, and so, after a few happy hours with our friends, we find all this fussing about the justification of causal inference to be "strain'd, and ridiculous." It is for this reason that Kemp-Smith called Hume's account a theory of "natural belief."
When Hume turns to the second big topic of Book I of the Treatise, our belief in the continued and independent existence of objects, the story becomes a very great more complicated, and to my mind at least, more interesting as well. The entirety of Hume's discussion occurs in several locations in Book I, but in a desperate effort to keep this tutorial from ballooning out of all proportion, I shall confine myself to the primary discussion, in Section xiv of Part IV of Book I, "Of Scepticism With Regard to the Senses." This section is far and away the longest in Book I, running some thirty-two pages in the Selby-Bigge edition. [A mere clearing of the throat for some philosophers, but in a work by Hume, a veritable monograph.]
Before beginning my exposition and analysis, let me make a few personal remarks. I first read this section in September 1952, as a seventeen year old Sophomore in Henry David Aiken's course on Hume at Harvard. At the time, I was of course completely innocent of anything having to do with the mental development of infants, any memory of my own early development having receded into the mists of time. It was not until almost twenty years later, when I spent endless happy hours with my two baby sons, that I realized how brilliantly Hume had reconstructed the process by which the infant acquires a conception of the world. Needless to say, Hume had no such experiences on which to draw, having lived his life as a bachelor in an age when even married fathers saw little of their infant children. How on earth he got so many things right is a permanent mystery to me.
In preparation for the writing to this next portion of my tutorial, I took a few moments to review the succession of arguments in Section xiv. It has been half a century since I have done so, and the pages, somewhat yellowed into a pleasant cream color, are crisscrossed with my underlinings and marginal notations in both red and black pen. The argument is quite the most complex of any in Hume's writings, and it is, I think, important to explain it both accurately and in detail. I have decided therefore to pause before launching on this most important part of the tutorial. I shall fly to Paris tomorrow, taking with me both my copy of the Treatise and also my copies of the Enquiries and the Dialogues. After I have had time to review the argument of Section iv, I shall pick up the thread of my exposition.
While I am travelling, you may amuse yourselves by watching the first of the Fall Republican debates.