Know the Arguments for Skepticism and Common Sense

The rationalists relied on reason, not sensory experience, to explain the world. In turn, the empiricists—John Locke, George Berkeley, and David Hume—argued that knowledge comes from experience, not pure reason. Taken as far as logic allows, that entails some astonishing claims about reality.

Primary and secondary qualities

For Locke, primary qualities exist in the world, and secondary qualities in the perceiver. Solidity, extension, shape, motion, number—these exist whether they’re perceived or not. But attributes like color, sound, and scent exist only when perceived; there can be no image without an eye. (He didn’t reject reason altogether; rather, he thought that knowledge comes from the application of reason to sensory data.)

Berkeley, moved by Locke’s arguments regarding the uncertainty of secondary qualities, went further: he rejected Locke’s primary qualities, too. Berkeley thought that the distinction between qualities invites all sorts of skepticism. If we know only our own ideas, how can we trust them without ever comparing them to unmediated reality?

Perceptions, not material objects

The solution is simple: deny the existence of matter. If an apple is not only our collection of perceptions but also a material object, we may doubt that object, and such doubt is abhorrent to common sense. But if we define the apple as nothing more than our perceptions, it is beyond doubt.

The world doesn’t exist on its own, Berkeley argued—only perceptions do. Being is nothing more than being perceived.

Do objects come in and out of existence as we perceive them? Not quite. God always sees all things; thanks only to his perception, objects persist.

Hume’s doubt of the self

Hume, the most rigorous of the empiricists, developed Berkeley’s claims against the world to their logical end. People, he argued, “are nothing but a bundle or collection of different perceptions, which succeed each other with inconceivable rapidity, and are in a perpetual flux and movement.” Since there is no perception of self, there is no self.

This has some incredible consequences:

• It invalidates Descartes’ “I think, therefore I am,” which now merely assumes the “I” it would prove.
• It erases the distinction between self and world, which had so long dominated Western thought.
• It precludes the soul.

But that’s ridiculous!

Hume took empiricism so far that, for most people, it became unbelievable. In turn, Thomas Reid argued that belief in the world is the basis for meaningful philosophy—that if you don’t believe in the world as perceived, philosophy is useless. The difference between object and sensation, he argued, is obvious to common sense. In response to Hume’s doubt of the self, Reid noted that, in order to talk about philosophy, you must believe that you’re talking with another person. If you don’t, you’re insane, and not worth engaging in conversation. Refreshing, no?

On Reid’s common-sense foundation, Alvin Plantinga and Nicholas Wolterstorff developed the modern notion of Reformed epistemology, which defines belief in God as “properly basic”—belief that need not be proven from other truths. Despite the lack of irrefutable arguments for other minds, we believe in them; believing in God is just as reasonable.

Understand skepticism and common sense

Together, the Classics in Empiricist Philosophy Collection and The Works of Thomas Reid give you Locke’s, Berkeley’s, Hume’s, and Reid’s essential arguments, all searchable and cross-referenced. You’ll know the evidence for and against empiricism and common-sense philosophy, and you’ll understand Reformed epistemology’s foundations.

Keep reading—now that you know the empiricists, who were the rationalists?