Hume's Ideas about Necessary Connection

217 HUME'S IDEAS ABOUT NECESSARY CONNECTION 1 . Introduction Hume asks, "What is our idea of necessity, when we say that two objects are necessarily connected together"? He later says that he has answered this question, but it is difficult to see what his answer is, or even to see precisely what the question was. Currently there are two main ways of understanding Hume's views about our idea of necessary connection. These interpretations divide on the question whether Hume allows that we can speak meaningfully of an objective and necessary connection between two events. The one interpretation, which I will call epistemological, says that Hume does allow meaning to that phrase. On this view, justification is the only topic of Hume's negative message about necessary connection. We can mean what we say when we talk about necessary connection, but we cannot justify what we (meaningfully) say. That, according to this interpretation, is the negative outcome toward which Hume aims his investigation of the origin of our idea of necessary connection. He isn't denying we have that very idea; he is denying that its origin allows us to justify applying it to anything. The other interpretation, which I will call psychological, says that Hume does not allow meaning to the phrase, "an objective and necessary connection between two events." According to this interpretation , once we see the origin of our idea of necessary connection, we realize that we cannot mean by "necessary connection" what we thought we meant. Those words allow us to speak only of a certain 218 feeling in our minds, not of an objective feature of the world. Of course, the psychological interpretation partly resembles the epistemological one: it, too, denies that we can justify saying objective necessary connections exist. But on the psychological interpretation this follows a fortiori from the central negative claim, a claim which itself concerns meaning, not justification. In what follows, I will present these two interpretations more carefully and critically, and then I will advance my own. I think Hume was trying to express a view very different in kind from either of the two I've just mentioned. I think we can get a good idea of the kind of view Hume had by looking at Newton's treatment of gravitational force. Roughly, Newton thought that while there certainly are gravitational forces in objects, we can say nothing about them except that they are whatever it is that accounts for a specific set of observable regularities . Hume's views about necessary connection, or causal power, are roughly parallel. He does not doubt that we may speak meaningfully of objective necessary connections — rE we mean just some unknown quality in objects that underlies the constant conjunction of their sensible qualities. Inevitably we try to mean something more than this, but any such attempt is doomed to failure. Showing that we cannot mean something more is the point of investigating the origin of the "idea." I will be arguing that with this interpretation we can handle the sets of texts and problems that undercut the prevailing two interpretations , and reconcile those sets of texts with one another, despite their apparent inconsistency. This interpretation also has the advantage of attributing to Hume a view closely connected with a 219 distinctively eighteenth-century way of setting up these problems. Finally, I think the interpretation brings out nicely an instructive and central failing of Hume's views about necessary connection. 2. The Epistemological View Although there are hints of this kind of interpretation in other books, it is really articulated and defended only in Barry Stroud's book, 2 Hume. In what follows here, I mean to be sketching out and commenting on that interpretation. Hume wants to find out what our idea of necessary connection is. He conducts his investigation according to the dictum, "as we have no idea, that is not deriv'd from an impression, we must find some impression, that gives rise to this idea of necessity, if we assert we have really such an idea." (T 155) He argues, of course, that among our experiences of causes and effects, there are no impressions of necessary connection. Our experiences of...