As Aristotle might remind us, “reason” is said in many ways. All forms of reason are potentially valuable, but there is a very important distinction between what I’ve been calling the ethical reason that is intimately involved with who we are, and other forms that are more like tools we can use. Also, ethical reason relies on concrete judgments of things, rather than formal manipulations.
In some ways — in terms of the role I see it playing — ethical reason is more like what some people have called “will”. I prefer to avoid the term “will” because it is too often associated with an arbitrary power of decision. I do very much think of ethical reason as the thing in us that ultimately decides things large and small, but the kind of decision involved is always at least implicitly ethical (concerning what we “should” do), and therefore by no means arbitrary.
Common complaints against “reason” concern what I would call what I would call a usurpation of the place of ethical reason by the tool-like kinds of reason, or claims made on their behalf. Contrary to the claims of a certain ill-conceived modernity, tool-like reason can aid us in utilitarian calculations that may help inform decisions, but cannot by itself provide an adequate basis for decision, which is always ultimately ethical.
Whereas tool-like reason aims at precision, ethical reason is maximally inclusive in what it takes takes into account. This inclusiveness is its strong point, but at the same time makes it especially fallible. Due to the fact that we are situated beings in the world, there is no such thing as an infallible decisionmaking process we could use. Aristotle already pointed out that ethical reason is less precise than other forms. Tool-like reason achieves its precision by excluding considerations that ethical reason cannot ignore.
Because of this, concrete realizations of ethical reason can be better or worse. In general, human beings are called rational animals not because we are perfectly rational, but because we have the capability for reason. Especially in the case of ethical reason, that capability is always a matter of degrees. We all use it all the time, and do better or worse. We can also learn or be inspired to do better than we did before.