In a wonderful book “The Undercover Philosopher”, the author, Michael Philips, writes on rationality.

“How skeptical and pessimistic should we be about our attempts to understand the world?  This is the sort of question that gets asked at not very useful academic conferences. On one side of this debate are the skeptics. Skepticism about rationality has a long and distinguished pedi­gree in the Western tradition. Although Plato believed that rea­son could unveil the essence of all things, he also believed that reason was a hothouse plant that needed constant nurturing, and that it could get that nurturing only in a utopian political or social environment. In actual societies, it tends to be trampled underfoot. St. Augustine, strongly influenced by Plato, intro­duced a still more pessimistic picture into mainstream Christian theology. According to Augustine we are weak and corrupt heirs to Adam's sin driven by greed, pride, and bodily appetites, all of which distort and dominate our thinking. We cannot rely on ourselves to find truth. We must rely on the grace of God. A more secular tradition of skepticism with ancient roots came to full flower in the last century, in response to the massive organized madness of those years (the trench warfare, the genocides, the totalitarian propaganda, the religious fundamentalism, and all the rest). This tradition attrib­utes the causes of irrationality to hegemonic social and economic forces (the Frankfurt School, Foucault, and others), psychological mechanisms (Freud and the Freudians), and even language itself (Derrida and his followers). They come together in various versions of post-modernism, which, in its more dramatic versions, attacks the very idea of an accurate view of the world. Because we are "situated" by our historical position, our culture, our religion, our ethnicity, our class, our gender, and even our language, post-modernists argue, we are forever limited to partial and distorted perspectives.

The apostles of rationality also have a distinguished pedigree. Aristotle famously defined human beings as rational animals. According to his picture, every normal, well-raised member of a well-ordered human community will become rational in thought and action. This picture of human nature entered the Christian tradition through St. Thomas Aquinas, probably the most influential theologian in the history of Christianity, who consistently refers to Aristotle "the Philosopher." According to St. Thomas, reason is a God-given natural power that is fully capable of understanding the nat­ural world and even certain aspects of the divine. This opti­mistic picture of reason has many other sources as well. Descartes, Leibniz, and Spinoza argued that we can under­stand the fundamental truths about the nature of the universe by reason alone. Economists since Adam Smith have based their understanding of markets on the assumption that we make rational economic choices. And positivists since Comte have argued that we can discover truths about human societies and the natural world by applying the method of science. Philosophers of action also tend to be defenders of the more optimistic view. Despite all the madness, chaos, and confusion in the world, they argue, we are purpose-driven creatures who act to promote our interests or satisfy our desires. We do this thousands of times each day. All other things being equal, if I want to leave the room, I go to the door. If I want to open the door, I turn the knob. One way or another, rationality manifests itself in every purposeful act (even by lunatics).

These debates between the rationalists and the skeptics tend to be formulaic, pointless, and tiresome. The deflationary truth of the matter is that there are ways in which we are rational, and ways in which we aren't, and that our capacity for and use of rationality may vary with our circumstances. So, instead of arguing about whether human beings deserve some ill-defined honorific like "rational animal," we would do better to investi­gate how and when we think well, and how and when we don't. Thinkers on both sides of the issue are well stocked with examples. This book focuses mainly on ways thinking goes wrong. But it is important to remind ourselves how often thinking goes right. It's a good bet that even most skeptics get X-rayed to check for broken bones, fly airplanes to travel, have high-speed internet connections, and so on. But how can one trust these technologies without trusting the theories and beliefs on which they are based? Did we just get incredibly lucky?

That said, both sides of this debate have interesting and com­pelling points to make. Their debates are tiresome because they make them over and over again and fail to engage each other. What is needed, philosophically at least, is a theory of know­ledge that synthesizes the strong points of each side while tran­scending the opposition (as Kant synthesized the strong points of rationalism and empiricism in the eighteenth century). How can we do justice to the obvious limitations imposed on us by history, culture, race, class, gender, and personal circum­stances while at the same time acknowledging our evident capacity to learn about the world? This, I think, is among the most pressing philosophical questions of the present century.”