Remote and Proximate Causation

Here is a very helpful passage for understanding what St. Thomas means by remote and proximate causation:

Now that we have seen that there are four causes, the efficient, material, formal, and final, we should observe that each of these causes can be analyzed in many ways. We speak of something as a prior cause and of something else as a posterior cause. For instance, we say that art and the physician are the cause of health: art being the prior cause and the physician the posterior one. The same distinction applies to the formal and the other causes. Observe that we should always reduce a question to the primary cause. For example, if the question is: Why is this man healthy?, the answer should be: Because a physician has cured him; and again: Why did the physician cure him? Because of the art of healing which he possesses.

Note also that the so-called proximate cause is the same as the posterior cause; and the remote cause is the same as the prior cause. Hence, these two analyses of the causes - sometimes as prior and posterior, sometimes as remote and proximate causes - mean the same thing. Moreover, it is to be observed that, in all cases, that which is more general is called the remote cause, while that which is more special is the proximate cause. Thus, we say that man's proximate form is his definition, rational mortal animal, but "animal" is a more remote form, and "substance" is still more remote. Indeed, all higher things are as forms to lower things. Likewise, the proximate matter of a statue is bronze, the remote is metal, and still more remote is body.

-- Aquinas, On the Principles of Nature; this portion taken from Bourke, The Pocket Aquinas, pp. 73-74 (italics in original; bold added).