The true is what is. – St. Augustine.

In his Essay Concerning Human Understanding, John Locke makes this curious statement, “Our business here is not to know all things, but those which concern our conduct.”1 Why would Locke make such a statement in a work about the sources, nature, and validity of human knowledge? What, if any, is the connection between ethics and epistemology? Anyone familiar with Locke’s essay knows that ethics is not his central concern and yet he makes this statement which seems to put human conduct at the center of his inquiry.

A correct understanding of metaphysics will help us understand the relationship between how we know things and how we should behave but first we should look at the classical distinction between theoretical knowledge and practical knowledge. Although he does not exactly say this, Locke is getting at the distinction between theoretical and practical knowledge and how they might be related. These categories come to us from Aristotle. According to Aristotle, theoretical knowledge has to do with investigating things like metaphysics, the nature of the person, whether or not there is a God, the ultimate causes of reality, and transcendent truth such as the good, true, and beautiful. Practical knowledge includes pursuing life deliberately towards a good end (ethics), fulfilling one’s vocation wisely, and knowing how to do basic things like changing a tire on a car, building a house, or engaging in a craft.

While I think important connections exist between particular beings (automobile tires) and Being itself, I believe Locke is pointing us to the epistemological aspect of metaphysics and human conduct. After all, if ethics and human conduct is an important concern in our lives (and I believe it is), we must first understand the nature of human beings and the world we live in. If we do not understand the metaphysical nature of what it means to be human, we are likely to get what it means to live correctly wrong. This is one area where theoretical knowledge and practical knowledge go hand in hand.

Philosopher Daniel Sullivan puts it this way, “To judge rightly of human actions, therefore, we have to know what human nature is and its place in the scheme of things. Human nature, then, as seen by reason in its right relation to all reality, will be the test or standard by which we judge the morality of our actions.”2

Locke, therefore, wants us to understand that if we know the structure of reality correctly, we will have a better chance of discovering correct human conduct. I believe that metaphysics, epistemology, and ethics are related. Metaphysical knowledge is not entirely theoretical and ethics is not completely practical (it rests on prior and more ultimate concerns). What Locke helps us to understand is that even knowledge and ethics must have a metaphysical foundation.

Of course, Locke was not completely right in his epistemology and he makes mistakes. His rejection of innate ideas puts him at risk of being an anti-essentialist. Locke was a much better political philosopher than an epistemologist. However, he raises important concerns about what it means to be human and how one should interact with the world.

To read more deeply on this topic see:

Daniel Sullivan, An Introduction to Philosophy: Perennial Principles of the Classical Realist Tradition. TAN books, 2009.

Ed. L. Miller, Questions That Matter: An Invitation to Philosophy (any edition is fine).

Louis Pojman, Ethics: Discovering Right and Wrong. Wadsworth, 1995.

1. John Locke, An Essay Concerning Human Understanding, Great Books of the Western World, vol. 33 (Chicago: Encyclopedia Britannica, Inc., 1993), 95.

2Daniel Sullivan, An Introduction to Philosophy: Perennial Principles of the Classical Realist Tradition, (Charlotte, North Carolina: TAN Books, 2009), 150.