Toward the end of the first part of the Philosophical Investigations, Wittgenstein writes:

This passage is often credited with having prompted contemporary approaches to action theory in which philosophers proffer theories of the ostensibly missing ingredient(s) that would turn “mere behavior” into “full-bodied action.” But the question, asked by an imagined interlocutor, evinces what Ryle called a “category mistake” and is one that, as we shall see, Wittgenstein rejects. It is not an appeal for a theory of action requiring philosophers, cognitive scientists, or neuroscientists to answer.

Let us examine what I consider to be an insoluble predicament for the standard answers. We are understandably tempted to say that the difference between my having raised my arm and my arm's rising is my having willed it, intended it, or acted on reasons for doing it in the first case but not in the second. Although (as we shall see) there may be no harm in saying this in order to signal an important difference between voluntary or intentional action, on the one hand, and involuntary or unintentional behavior, on the other, trouble begins when we attempt to construe the description “having willed, intended, or acted for a reason” as indicating a prior or concomitant mental action or mental cause. This is, however, what many action theorists have taken to be suggested by Wittgenstein's rhetorical question. What is left over, some suggest, is an extra ingredient—a causal factor—which, when added to my arm's rising, yields the raising of my arm.

If, however, such supposed occurrences as intending, willing, or acting for reasons are actions performed intentionally, voluntarily, or for reasons—such as when I put my mind to concentrating hard—then, even if this were sufficient, it would simply push the problem back. For the question that seemed to require an answer in the first place would presumably require one here: if intending or willing, for example, were themselves doings as opposed to mere happenings, then what would make them so? We cannot suggest that all voluntary or intentional doings must be preceded by acts of willing or intending, however elusive, without embarking on a vicious regress.