Thursday, July 03, 2003

Further Comments and Questions about Causality and Inference

Comment 1: Even if you are a believer in causation -- even if you believe that events in the space-time continuum can and do influence later events --, you may reject the intimation in my last blog that you (as a believer in causality) must believe in some underlying mechanism, some device or process that lies in some substratum, in some stratum below the level of phenomena. You might protest that the sort of notion of causation that I seem to be peddling is both unnecessarily mechanistic and unnecessarily reductionist. You might argue that you are entitled to believe in causation even if all that you believe is that phenomena can be explained by principles that express relationships between events in space and time and that there is no need to suppose that these causal principles or explanations somehow exist in or beneath the events that they describe. It is sufficient, you might say, that the "laws" -- or, better said, principles or law-like statements -- that you embrace -- such as [F = MA] or [e = m(c-squared)]? -- predict the relationships among phenomena in a wide variety of circumstances.

Question: If this is what you think, why is it that causal "laws" or principles often or ordinarily do seem to rest on some image of a mechanism or real process that generates or controls the phenomena that one both uses as evidence and that one wants to explain -- e.g., an image such as a spinning atom surrounded by electrons in odd orbits; an image of a double helix? Granted, these "spatial" images sometimes or often collapse -- they come be seen as inadequate -- as scientific understanding progresses -- but perhaps this merely shows that science progresses. Is it the case that the progress of science often involves, not the elimination of spatial images of (hidden) processes or mechanisms, but, rather, the modification of old images or their replacement with new and better ones? (So: Kepler posits elliptical orbits rather than circular ones.) So is it true, after all, that a belief in causality involves or requires, at least sometimes, a belief -- a provisional belief, to be sure -- in the existence of underlying mechanisms or processes; and is it true that it cannot be said that "causal mechanisms" are merely or nothing more than disguised non-spatial principles that describe observed regularities or phenomena in nature? If one is to arrive at causal explanations, is it necessary to have a kind of "persuasive local ontology," a kind of vision of how (some) things just must work? (By the way: Why should we presume that spatial representations are not "principles"? Graphs are "spatial" {at least in two dimensions, and graphs can be multi-dimensional} -- but properly-constructed graphs are rigorously logical things. If they aren't "principles," what are they?)
Counterpoint: Would one say of a causal explanation for, say, a social phenomenon -- e.g., "gang behavior" -- that it is necessary to have or develop a spatial representation or image of the mechanism or process that causes or influences this kind of phenomenon? (Answer: probably not, which may be a reason for the persistent belief in the existence of "souls." The causal explanation {if any} in this sort of situation might be in terms of the incorporeal principles -- principles and rules that exist but that cannot be seen (even in the mind's eye) -- principles that, it might be supposed, animate or govern (to some extent) the behavior of the members of a gang and the gang itself.)
Comment 2: Causality implies that prior events influence future events. But human beings (and perhaps other animals) peer into the future and allow their vision(s) of the future -- of future events -- to influence their actions in the present. Does this mean that the future influences the present? If you are a believer in unidirectional causality, you will reply, "Certainly not!" You will say that the future influences prior events only in this sense: people's projections at time t of future events influence their decisions or choices at time t + 1, which in turn presumably influence yet later events. Hence, there is no violation of the premise that causality runs only in one direction and -- to be sure -- from the "past" to the "future." (You say my last statement is circular? I know the past, present, and the future when I see it ["them"?], b'gosh!)

Comment 3: [I am preparing a comment -- a question, a hypothetical problem -- involving the "variables" (1) gang membership, (2) burglaries, and (3) tattoos. And at some appropriate point I will try to confound everything by mentioning the additional variable or factor, (4) the drinking of gin. This problem, if I can construct it, will raise two basic questions: (a) Can any set of numbers (alone) establish any causal relationship(s) among these three or four variables or factors?; and (b) If not, is evidence of the existence of any one of these three or four factors necessarily bereft of any probative value for any other factor (e.g., the commission of a burglary vel non)? But I do not yet have a suitably-crafted version of this hypothetical problem in hand -- and it is possible that I won't have the time to formulate it properly. Perhaps you can do so, Gentle and Wise Reader? (One of the matters or questions I have in mind is Judea Pearl's "d-separation" criterion for inferring causes from statistical data.)]

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