What is it that is supposed to be so unobservable about causation? This question has nagged at me since my days as an undergraduate (and there has recently been a lot of discussion of it over at Brains, which inspired me to post on it). It had always seemed to me that the causal relation was entirely observable. We even have evidence that we have been observing it since before we could talk. For instance from the cradle we witness the passing of the sun behind clouds and the subsequent darkness, we witness objects falling to the ground, we witness that motion is attended with sound, and etc. Nor are these examples special; cases like these can be multiplied indefinitely. We can see water extinguish flame. While walking about I kick a stone and see my foot cause the rock to begin its trajectory. I can see the acid turn the litmus paper red. Pointing a magnifying glass at a piece of paper on a sunny day will cause the paper to smoke and turn brown, eventually catching fire. A small dog biting at my ankles will cause a pinching sensation and perhaps annoyance! I take these to be examples of seeing A cause B, seeing A causing B and feeling A cause B.
So why think that the causal relation is unobservable? I take the canonical text on this to be Section seven of Hume’s Enquiry. For instance in paragraph six of that section he says,
When we look about us towards external objects, and consider the operation of causes, we are never able, in any single instance, to discover any power or necessary connexion; any quality, which binds the effect to the cause, and renders the one an infallible consequence of the other. We only find, that the one ball does, actually, in fact, follow the other. The impulse of one billiard-ball is attended with motion in the second. This is the whole as it appears to the outward senses. The mind feels no sentiment or inward impression from this succession of objects: Consequently, there is not, in any single, particular instance of cause and effect, any thing which can suggest the idea of power or necessary connexion. (Hume 1999)
No doubt it was passages like this that lead to Kant’s rather rude awakening from his dogmatic slumber. It seems to me to have plunged us into one. In the above passage, which is completely typical of that section, Hume seems to be saying that since we cannot see that the connection between these events is necessary, which is to say that we cannot see why what happens is the ‘infallible consequence’ of the first event as opposed to some other event, there is no way that the idea of causation could be taken from anything perceptible in the outside world. It follows from what he says that the causal relation is not observable; something that makes no impression on the human senses would have to be. The intuition that we have to see the necessity of the causal relation in order to see it at all has guided discussions of the observability of the causal relation. It seems to me that Hume here fails to make a distinction between what we observe and how we analyze what we see. What we observe is a relation; it is when we turn to how to characterize that relation that necessity is involved.
As C.J. Ducasse pointed out, Hume’s claim about the unobservability of causation would be true only under “the assumption that a ‘connection’ is an entity of the same sort as the terms themselves between which it holds…” (Ducasse 1993, p 131). Hume’s mistake was to look for the sense impression of a relation. This we will not find unless relations exist in the same way as the things they relate. But the relation between two objects is not itself a third object! Consider two objects, one to the left of the other. We do not see the relation ‘to the left of,’ but rather see one thing as being to the left of another. It does not even make sense to ask ‘what does the relation ‘to the left of’ look like?’ If asked this question all we could do is describe the position of the objects along with the definition of ‘left,’ and ‘right.’
Any further questioning about what ‘left of’ looks like would betray a category mistake. That is, mistaking a relation for an entity of the sort that it holds between. By way of comparison imagine Hume arguing that ‘left of’ is unobservable. I mean all we see is object A and Object B no where is there an impression of ‘left of,’ and so strictly speaking our idea of ‘left of’ is meaningless. But this is ridiculous! The argument seems to work against any relation and so proves too much.
When we see one ball hit the other we observe that the two balls are related, one causes the other to move, but we do not see that the relation is necessary even though it is in fact a necessary one. Just as we can see X moving without seeing that X is going 22 MPH, or we can see X being 3 ft away from Y without seeing that X is 3 ft away from Y. Despite the fact that I do not see that X is three feet from me I do see the relation ‘3 ft away from,’ I just don’t know that it is this relation. We see relation X qua relation while not seeing that X is such and such a relation. So on the view I am advocating we see A and we see B and we see A cause B but whether or not we see THAT the relation is necessary is a different question.
Richard Brown 
In response to the post at Philosophy & LIfe which is a response to this post (which has the annoying feature of not letting you pst without a google/blogger account)
Hey thanks for reading and for the post, but Brown feels that you are missing his point.
You seem to miss the distinction that I made between seeing the causal relation and seeing THAT the relation is necessary. So, I agree with you (and Hume)that I do not see THAT the relation is necessary, but what does that have to do with seeing the relation in the first place.
And it may be true that I cannot point to the relation and say ‘there it is’ but so what? That seems to be generally true of relations, so why should the causal relation be any different.
I wonder if maybe Hume thought that one can’t observe causation because he considered necessity as the essential characteristic of causation.
There are two possibilities that come to mind connected to this
1.If you can’t see that the connection is necessary, you can observe a connection, but you will never be able to observe it AS causation. (as that necessary property of being necessary doesn’t appear)
2.As the necessity can’t be observed, and as necessity is causation’s necessary property, one can’t come to the idea of causation from observing.
Having said that, I agree with you that causation seems to be observable, and if by definition it shouldn’t be than there is something wrong with the definition.
Yeah, that’s a good question. I do think that Hume thinks that. He says that the idea oc causationi sthe idea of a necessary connection between events, and we don’t see that so we don’t see causation. But, again, I think that is just an argument that we don’t see that the connection is necessary.
As for 1, I think that depends generally on what you think ‘observability’ entails. If you think, as I sometimes do, that we can actually see an electronin the cloud chamber, then perhaps we can come to see that the causal connection is necessary…but to be honest, I go back and forth on this issue…
As to 2. Maybe if the necessity of the relation can’t be observed then that means that we don’t get it from experience, but that might be a good thing since there are lots of studies in developmental psychology that suggest that the concept of causation is innate.
Lovely point, Richard. And did Hume think that we could see a billiard-ball? He seemed to assume that, although if we only see the colours and shapes, and posit (correctly) that they are evidence of a billiard-ball, then that seems analogous too.
Hi Enigman, thanks for the comment.
That’s a good point about Hume’s theory of perception. He certainly talks as though we see the billiard ball, I mean that is what the word ‘impression’ conjures up. We have this picture that the object itself makes the impression, but it is not clear that that is what Hume means at all. Since Descartes most philosophers had endorsed the view that our ideas were really judgments based on sensory experience (the empiricists, of course, thought that ideas resembled objects, whereas rationalists like Descartes, and later Kant, denied that). But there is a difference between the billiard ball and causation for Hume in that the former but not the later can be traced back to an impression. The relation between the impression and the object is a different question all together (one that I, personally, think that a Kripke kind of story can be given).
But, I just realized you were probably replying to the last comment and not the post…ah I see…then yes I see the analogy that you are making. In the case of seeing objects, we say that what counts as seeing them is making a correct judgment based on our impressions, so we can say the same thing in the causal case; what counts as seeing the necessary connection is a. seeing the connection, and b. judging (correctly) that it is necessary. That would mean that if one accepts a Humean theory of perception we should be more inclined to think that we could come to see THAT the connection was necessary. Nice point. Is this what you meant?
just now i flipped a switch in my room. two things (among others) happened immediately after i did this: (1) the lights went on, and (2) a bird chirped outside my window. we typically think of the flip of the switch as being causally linked to (1) and not to (2) — but why? did i “observe” anything which would indicate that there is a link between the switch and (1) but not (2)? hume would say not. in both cases, all i observed is that one event followed another.
what do you “observe” that allows you to dinstinguish between causality and mere coincidence?
in fact, the only way we could make such a distinction between (1) and (2) is by saying that the lights seem ALWAYS to go on after i flip the switch, whereas birds do not always chirp when i do this. hence hume’s contention that we call “causality” is just the observation of constant conjunction. the conjunction between the flip of a switch and a light’s illumination may be more consistent than that between the flip of a switch and a bird’s chirping, but there is not a difference in kind between our perception of either phenomenon.
(this of course leads into the problem of induction; i.e., why suppose that two events that have been conjoined in the past should be conjoined in the future?)
Hi Ace, thanks for the comment!
I have a couple of things to say.
1. I agree that we do not se the necessary-ness of the relation, and it is possible that the relation may not be necessary (that is, it may all boil down to constant conjunction). Either way this is a seperate question from the question of what gets observed.
2. As for the other point about how we can tell the difference between causation and corelation, or even coincidence…I don’t know…but what ever we say notice that this is a general problem for perception, not just the perception of the causal relation. I mean, how do you tell the difference between a red wall and a white wall with a red light shone on it? Is there some perceptible thing that will cue you to the difference? I don’t think so. But this is no reason to despair because our sensory systems are generally reliable and so we have a defeasable justification to believe that things are the way that they seem to us.
3. One reason why I might think that turning the light switch matters, and not the bird chirping, is that I can set up experiments where I control the circumstances and thereby narrow down what it is that is doing the causing. At any rate, it is fairly easy to rule out the bird…This is actually the way that science usually works, we observe how things work and then devise ways to interfere with the thing of interest to see what happens.
Richard,
I was thinking about the object permanence as a theory (re our discussion on Brood Comb), and how it connects to this issue.
With the object permanence one can give (among others) those two possibilities:
1.The objects are seen (or perceived in general) qua permanent objects.
2.What one sees is time-slices (whatever this means, I haven’t seen those yet 🙂 ), and the objects are theoretical constructs based on built (naive) physical theories
It seems that one can do analogous division of options for case of causality (for making the case even more analogous one can point to Baillargeon researches that indicate that at 2.5 months, infants expect for a thing to be displaced when hit by another, which is also the time where they seems to be aware of object permanence). The options would be like this:
1*.One object hitting another is seen qua hitting, or qua event in which one object affects another or qua causal relation.
2*.What is seen is merely objects and their movement, or time-slices, and that one object hits another is a theory that is developed.
I wonder where would you stand if things are put like that… Would your saying that causation is observable is along 1*? Or would you go with something like 2* and try to say that causation is observable because the theory is somehow added to the perception?
Hi Tanasije, interesting comment! Thanks.
I think that you are on to something in the comairison that you are making. I guess I would opt for option 1*, I think something like 2* is what Hume and Quine might think, but it is not something that I like. I am very anti-time-slice myself…
if an event A is immediately followed by events B and C and “causes” one of them (but not both), and you can’t tell after a single trial which of B and C is the causal result of A, then i don’t think you can be said to have “observed” causality. you talk about experiments to distinguish between mere correlation and causation, but that just plays into hume’s formulation — i.e., that we do not “observe” causality but rather assume a necessary connection between events which we observe to be constantly conjoined. (all this of course leads into the problem of induction.)
to reiterate: how can you be thought to “observe” causality in any way other than that which hume describes if you need repeated trials to infer the causal link?
Hi etrigan,
Thanks for the comment!
Depending on the details of the situation I guess I would say that in the case you describe it <em?looks like A causes B and C. The experiment would be done to find out whether or not it actually does cause both or only one. So, for instance, if we found out that B was just a one time thing we would likely conclude that though it looked like A caused B in the first experiment it in fact did not it only causes C. This sort of thingseems to be what scientist do all day long in the lab (of course they do other things, my point is only that this is one of them). I think we use this ‘looks like’ talk all the time when we talk about causal relations. It looks like the bullet kills the guy but it is CGI etc…What I do not say you observe is the necessity of the relation. That is a seperate matter (according to me)…So, I don’t have to see that the table is 5ft to the left in order to see it to the left and I o not have to see that the relation is necessary in order to see A cause C. The fact that there are cases where we can be fooled (i.e. where somthing looks like it causes something which it doesn’t in fact cause) seems to me to just be evidence that we are observing something. Compare: It is because I know what a red wall looks like that I can be fooled into thinking that a certain wall is red (as when say, it is really a white wall with a red light shone on it). Does that help?
Oooppssss!!! Damn you XML code!!!!!
Imagine a causal pair of events A->B, where A causes B.
What would be the difference, in terms of sense impressions, if A was in fact only correlated with B?
Hi Crosson,
Thanks for the comment!!
I don’t think that there would be a difference in terms of sense impressions…That is what I think Hume’s mistake is…why, do you think this matters somehow to whether or not we see the causation?
Sorry if this thread is no longer being checked, but I think that what is missing from your argument is that the term “cause” entails necessity. To claim that A causes B is to claim a relationship of necessity. That’s the actual difference between causation and correlation or coincidence. I don’t know how you can distinguish “we see A cause B” from “we see that the relation is necessary.” The example of seeing a ball that is 3 feet away without seeing that it is three feet away is different, because in that case we have an observational method of determining that x is 3 feet away – we can use a ruler.
[…] his blog post “What’s So Unobservable About Causation?,” Richard Brown posits that, contrary to David Hume’s views, causation is indeed observable; […]
Great food for thought, thanks Richard! I wrote an extended reply to this for a philosophy class I took at Hunter with Prof. Kivatinos. It’s posted at http://www.funintrouble.com/blog/david-hume-vs-richard-brown-observing-what-doesnt-exist if you’re curious.
I’m a little late to the party, but imagine we have two scenarios, one where a ball is rolled towards a stationary ball as described previously and one where the same thing occurs but the second ball is glued to the table and therefore doesn’t move when contacted by the rolling ball.
In the first scenario, we would say that the action of the rolling ball sufficiently caused the stationary ball to begin moving, however, the same thing happens in the second scenario yet the stationary ball remains stationary. Could we not then conclude that the moving ball in the first scenario is actually not sufficient? We might say that the sufficient conditions for movement are 1) to be contacted by a rolling ball and 2) not be glued down. As an additional question, would it make sense to say that the glue caused the second ball to remain stationary (essentially to do nothing)? Is that an idea that our minds can really process?
It hasn’t been discussed but we know that other causes could be sufficient in the way we first understood the rolling ball to be sufficient. Perhaps the wind or a human hand could cause the stationary ball to move. Likewise, there could be any number of reasons that the stationary ball remains stationary even if being struck by something else.
The point that I’m getting to is that no single cause, or in fact any number of causes, is sufficient or necessary to cause the stationary ball to move or remain stationary. If no cause contributes anything to necessity or sufficiency, how can we say it’s a cause?
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