Philosophical Empiricism

Empiricism is the philosophical stance according to which the senses are the ultimate source of human knowledge. It stands in contrast to rationalism, according to which reason is the ultimate source of knowledge. In Western philosophy, empiricism boasts a long and distinguished list of followers; it became particularly popular during the 1600's and 1700's. Some of the most important British empiricists of that time included John Locke and David Hume.

Empiricists Maintain That Experience Leads to Understanding

Empiricists claim that all ideas that a mind can entertain have been formed through some experience or – to use a slightly more technical term – through some impression. Here is how David Hume expressed this creed: "it must be some one impression that gives rise to every real idea" (A Treatise of Human Nature, Book I, Section IV, Ch. vi). Indeed – Hume continues in Book II – "all our ideas or more feeble perceptions are copies of our impressions or more lively ones."
Empiricists support their philosophy by describing situations in which a person’s lack of experience precludes her from full understanding. Consider pineapples, a favorite example among early modern writers. How can you explain the flavor of a pineapple to someone who has never tasted one? Here is what John Locke says about pineapples in his Essay:
"If you doubt this, see whether you can, by words, give anyone who has never tasted pineapple an idea of the taste of that fruit. He may approach a grasp of it by being told of its resemblance to other tastes of which he already has the ideas in his memory, imprinted there by things he has taken into his mouth; but this isn’t giving him that idea by a definition, but merely raising up in him other simple ideas that will still be very different from the true taste of pineapple."

(An Essay Concerning Human Understanding, Book III, Chapter IV)
There are of course countless cases analogous to the one cited by Locke. They are typically exemplified by claims such as: "You can’t understand what it feels like …" Thus, if you never gave birth, you don’t know what it feels like; if you never dined at the famous Spanish restaurant El Bulli, you don’t know what it was like; and so on.

Limits of Empiricism

There are many limits to empiricism and many objections to the idea that experience can make it possible for us to adequately understand the full breadth of human experience. One such objection concerns the process of abstraction through which ideas are supposed to be formed from impressions.

For instance, consider the idea of a triangle. Presumably, an average person will have seen plenty of triangles, of all sorts of types, sizes, colors, materials … But until we have an idea of a triangle in our minds, how do we recognize that a three-sided figure is, in fact, a triangle?
Empiricists will typically reply that the process of abstraction embeds a loss of information: impressions are vivid, while ideas are faint memories of reflections. If we were to consider each impression on its own, we would see that no two of them are alike; but when we remember multiple impressions of triangles, we will understand that they are all three-sided objects.
While it may be possible to empirically grasp a concrete idea like "triangle" or "house," however, abstract concepts are much more complex. One example of such an abstract concept is the idea of love: is it specific to positional qualities such as gender, sex, age, upbringing, or social status, or is there really one abstract idea of love? 

Another abstract concept that is difficult to describe from the empirical perspective is the idea of the self. Which sort of impression could ever teach us such an idea? For Descartes, indeed, the self is an innate idea, one that is found within a person independently of any specific experience: rather, the very possibility of having an impression depends on a subject’s possessing an idea of the self. Analogously, Kant centered his philosophy on the idea of the self, which is a priori according to the terminology he introduced. So, what is the empiricist account of the self?

Probably the most fascinating and effective reply comes, once again, from Hume. Here is what he wrote about the self in the Treatise (Book I, Section IV, Ch. vi):
"For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception. When my perceptions are removed for any time, as by sound sleep, so long am I insensible of myself, and may truly be said not to exist. And were all my perceptions removed by death, and could I neither think, nor feel, nor see, nor love, nor hate, after the dissolution of my body, I should be entirely annihilated, nor do I conceive what is further requisite to make me a perfect nonentity. If any one, upon serious and unprejudiced reflection, thinks he has a different notion of himself, I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continued, which he calls himself; though I am certain there is no such principle in me. "
Whether Hume was right or not is beyond the point. What matters is that the empiricist account of the self is, typically, one that tries to do away with the unity of the self. In other words, the idea that there is ​one thing that survives throughout our whole life is an illusion.