Reason and Knowledge

Class notes for 11 January

Main points

I had two main aims.

First, to characterize what is distinctive about causal relations for Hume. So, we spent a lot of time on what distinguishes the relations among ideas in column A from those in column B and on what distinguishes causal relations among ideas from the two other relations in column B.

To simplify greatly, I can imagine that two causally related ideas are not causally related (and vice versa). By contrast, the relations in column A are such that one cannot imagine that the column-A-related ideas do not bear the column-A-relation to one another; imaginatively changing the relation necessarily involves changing the related ideas.

Unlike the other relations in column B, the causal relation does not involve comparing ideas that are present in the mind before one thinks about the column-B-relation among them. Causal reasoning can lead us to have an idea that we think is causally related to another.

Second, I wanted to go over Hume’s famous argument about induction and the uniformity of nature in 1.3.6. We did this quickly and will begin with a more careful look on Thursday.

Distinguishing columns A and B

I said that one cannot imagine changing the relations in column A without changing the related ideas. That is what distinguishes the relations in column A from those in column B. (Note: this is a bit different from the way the Nortons describe the distinction. Compare pp. I24-5, that’s capital i, by the way)

Katie threw a tricky question at me. She took Hume’s example of two ideas (the sum of the interior angles of a triangle and the sum of two right angles) that have this relation to one another: “equal to”. She asked why we couldn’t change the relation of “equal to” to “greater than or equal to” without changing the related ideas.

True enough, there is no need to change the ideas. Very clever, Katie.

Here is a simple way of answering Katie’s clever query (provoked by a very helpful email from Matt Ishida).

When comparing two ideas by using one of the relationships in column A, changing the relationship such that the original comparison is no longer true must involve changing the ideas as well. This is not so with the relations in column B.

Thus, Katie’s example of substituting “greater than or equal to” for “equal to” does not conflict with Hume’s way of drawing the distinction, since that substitution does not involve saying that the original relation (equal to) is false.


Dasha and Justin pointed out some tensions concerning Hume’s characterization of the relations in column A. Specifically, Hume seems to say that thinking about these relations both does and does not involve reasoning. Here are some of the passages and my take on what is involved.

Here is one passage I referred to (the one that Dasha was looking for during class):

“And as the power, by which one object produces another, is never discoverable merely from their ideas, ‘tis evident cause and effect are relations, of which we receive information from experience, and not from any abstract reasoning or reflection.” (

Since that paragraph is about the contrast between the relations in column A and those in column B, I assumed that he meant that we receive information about the members of column A from abstract reasoning or reflection.

That means that he sometimes described our knowledge about the relations in column A as based in reasoning and sometimes he described it as not being based in reasoning. For example, under what I called the fourth difference between columns A and B:

“Three of these [four] relations [in column A] are discoverable at first sight, and fall more properly under the province of intuition than demonstration. … this decision we always pronounce at first sight, without any enquiry or reasoning.” (

I think this means he uses “reasoning” a bit loosely. However, when he’s being loose by drawing distinctions among the items counted as “reasoning,” he usually introduces some other vocabulary to mark the distinction among the items on the “reasoning” list. Here, it’s “intuition” and “without enquiry,” meaning we see the relation pretty much immediately, without a chain of thoughts as opposed to reaching the relation through a chain of thoughts. There is something similar going on in

So I think the looseness is relatively harmless, though it is something to keep our eye on. Sometimes, catching a philosopher doing something like this is a way of catching an equivocation that will be relevant for an argument. (“Equivocation” means using a single term with two different meanings; if one premise in an argument uses the term with one meaning while a different premise uses it with another meaning, the argument will not be valid, despite appearing to be valid). Other times, it just means that the author sees distinctions within a category.

A qualification

My characterization of what I called the fourth difference between the relations in column A and those in column B was a bit overblown. I put more emphasis on intuition than I would have liked to. The correct way of saying how the relations in column A are known is to say that they are known by intuition or demonstration: what is important is that they are known in ways that yield certainty.

Here is the relevant passage.

“Three of these [four] relations [in column A] are discoverable at first sight, and fall more properly under the province of intuition than demonstration. … this decision we always pronounce at first sight, without any enquiry or reasoning.” (

That means that only three of the four members in column A are discovered by intuition. The fourth is comparisons of quantity, proportion or number. Those can be known by demonstration as well as intuition. See the discussions of algebra and arithmetic.

Next time: section 6

On Thursday, 13 January, I would like to start with a more careful look at 1.3.6. In particular, I want to address two questions that were posed last time.

Katie on constant conjunction

The first, from Katie, concerned what exactly Hume means by a constant conjunction. She had noted that we make causal inferences between As and Bs even if the pairs of A-B we had experienced in the past had been interrupted. For example, I might see the hot sun, look at the table, the chair, the sink, and then notice that the butter is melted. From this series of impressions, I may very well draw the conclusion that the sun melted the butter.

She might have meant that our past perceptions had come in one of two patterns:


I think the first sort of case is no problem for Hume. As and Bs are constantly conjoined and, crucially, As always precede Bs (and not the other way around).

The second sort of case is a problem for Hume because the relevant ideas may not be contiguous in time or space: the sun is far away from the butter and my impression of the sun is not contiguous in time with my impression of the butter.

If Katie had the second sort of case in mind, she’s probably right: Hume should have dropped contiguity. As it turns out, that’s what he did in the Enquiry Concerning Human Understanding, his later, revised version of Book I.

Justin on justification

Gosh, alliteration is fun.

Anyway, Justin had asked whether 1.3.6 is concerned with the justification of our causal inferences (meaning ‘do we have good reason to make them’, ‘should we make them’, ‘are we right to make them’) or whether it is an attempt to explain how we do make causal inferences.

I think that’s a good question because the text is ambiguous.

For example, the Uniformity Principle isn’t the sort of thing that would enter into an explanation of how we actually think: children and animals make causal inferences but they don’t think of the Uniformity Principle while doing so. (Nor do adults, for that matter, but kids n’ critters seal the case.)

But the question is framed as an explanatory one. The question is “whether experience produces the idea [of a particular cause or a particular effect] by means of the understanding or imagination; whether we are determined by reason to make the transition [from an impression to the idea of the cause (or effect) of the impression], or by a certain association and relation of perceptions?” (

I would like to discuss that. In part, I think the answer has something to do with the fact reason is supposed to produce certainty or knowledge. ‘Certainty’ and ‘knowledge’ have implications for questions about justification. If I’m certain that the cat has one eye, then I can’t be shown to be wrong in believing that the cat has one eye and, in that sense, I’m justified in believing that the cat has one eye.