Any actual practice which involves adapting some means to an end, whether the end be deliberately adopted or not, is a case of activity being guided by a final cause. In nature, things which perform the same general function, live the same kind of life, or fill the same niche in ecological or meaning space (despite individual differences), belong to the same class because they share a common final cause. Peirce explains the difference between final and efficient causation in his 1902 ‘Classification of the Sciences’ (EP2:120). In this passage he is
engaged in tracing out the consequences of understanding the term “natural” or “real class” to mean a class the existence of whose members is due to a common and peculiar final cause. It is, as I was saying, a widespread error to think that a “final cause” is necessarily a purpose. A purpose is merely that form of final cause which is most familiar to our experience. The signification of the phrase “final cause” must be determined by its use in the statement of Aristotle [Metaphysics 44 b1 and 70 b26] that all causation divides into two grand branches, the efficient, or forceful; and the ideal, or final. If we are to conserve the truth of that statement, we must understand by final causation that mode of bringing facts about according to which a general description of result is made to come about, quite irrespective of any compulsion for it to come about in this or that particular way; although the means may be adapted to the end. The general result may be brought about at one time in one way, and at another time in another way. Final causation does not determine in what particular way it is to be brought about, but only that the result shall have a certain general character. Efficient causation, on the other hand, is a compulsion determined by the particular condition of things, and is a compulsion acting to make that situation begin to change in a perfectly determinate way; and what the general character of the result may be in no way concerns the efficient causation. For example, I shoot at an eagle on the wing; and since my purpose,—a special sort of final, or ideal, cause,—is to hit the bird, I do not shoot directly at it, but a little ahead of it, making allowance for the change of place by the time the bullet gets to that distance. So far, it is an affair of final causation. But after the bullet leaves the rifle, the affair is turned over to the stupid efficient causation, and should the eagle make a swoop in another direction, the bullet does not swerve in the least, efficient causation having no regard whatsoever for results, but simply obeying orders blindly.
Why is obedience blind? Because it doesn’t allow for learning from experience. When orders can’t be questioned, the meaning cycle at the heart of the guidance system is short-circuited. Of course there are situations where obedience is more ethically appropriate than learning, but one has to learn to recognize situations in order to choose the ethical response to them. Absolute certainty or trust in authority is likewise blind. Knowledge that can’t be tested can’t be trusted. A model that can’t be modified is not reliable.
Any practice undertaken consciously must have a telos, a final cause, but the practitioner’s attention has to be on the momentary current of actual events in order to flow with them and carry them forward in real time. The immediate sense of forward, of directedness (and not conscious awareness of a goal set in the projected future) is the feeling of flow, of living the time. So the ideal practice is not atelic but autotelic; it is alive to both final and efficient causes. Peirce explains how these complement each other:
Efficient causation is that kind of causation whereby the parts compose the whole; final causation is that kind of causation whereby the whole calls out its parts. Final causation without efficient causation is helpless; mere calling for parts is what a Hotspur, or any man, may do; but they will not come without efficient causation. Efficient causation without final causation, however, is worse than helpless, by far; it is mere chaos; and chaos is not even so much as chaos, without final causation; it is blank nothing.EP2:124