The Main Empiricists

John Locke (1632-1704)

Locke, considered the father of modern Empiricism, claimed that there are 3 types of knowledge:
1. Intuitive.
A form of knowledge that appears to be the most certain and obvious to us and the most difficult to doubt. For example, “I have a body”, “Black is not white”, and even, “God exists”.  Locke argued that these are so obvious that we accept them intuitively (
a priori knowledge or truth by definition.)
2. Demonstrative.
Demonstrating something by putting simple ideas together to form complex ones. For example, to compare the heat of the Sun with the heat of a fire, the demonstration shows that they are both made of similar substances (a posteriori knowledge because it may change).
3. Sensitive.
Knowledge that relies on the senses.  For example, in counting the number of chickens in a coup one is relying on sensitive knowledge. It is possible, as Descartes has shown, there could be an error. (a posteriori knowledge).

Locke’s philosophy of perception has been classified as Indirect Realism (‘representative realism’) as opposed to Direct Realism (‘na├»ve realism’).

The 'nature versus nurture' debate concerns the relative importance of an individual's innate qualities ("nature," i.e. nativism, or innatism) versus personal experiences ("nurture," i.e. empiricism or behaviorism) in determining or causing individual differences in physical and behavioral traits.

Locke termed the phrase tabula rasa "blank slate” - the view that humans acquire all or almost all their behavioral traits from "nurture".  He proposed that humans develop from only environmental influences. This question was once considered to be an appropriate division of developmental influences, but since both types of factors are known to play such interacting roles in development, most modern psychologists and anthropologists consider the question naive—representing an outdated state of knowledge.

In regards to political theory, John Locke taught that men naturally possess certain rights – life, liberty & property – and that a contract should exist between a government and its subjects: people give up a part of their rights in return for a just rule, and the ruler hold his power only so long as he uses it justly.  The American Declaration of Independence is largely influenced by Locke’s teachings.

Bishop George Berkeley (1685-1753)

Bishop George Berkeley (Bishop of Cloyne), was an Anglo-Irish philosopher who advanced a theory he called "immaterialism" (later known as "subjective idealism") which denied the existence of material substances.  His idealism took the view that the only things that exist are minds and their contents.  For example, a familiar object like a table is only an idea in the mind of the perceiver and cannot really exist without being perceived.

Immaterialism is a genuinely empiricist philosophy, since it begins with what we actually experience and claims to account for everything without making extravagant suppositions about unknowable entities.

Berkeley's Immaterialsim begs the philosophical question:  “Can something exist without being perceived?”  Like the question – “If a tree falls in a forest and no one is around to hear it, does it make a sound?”  George Berkeley developed subjective idealism, a metaphysical theory to answer this type of question, which he famously said, “esse is percipi” (to be is to be perceived). 

Berkeley claimed we can never actually experience the object itself. The main problem for idealists is that very often our perceptions correspond with one another.  If the world is full different perceptions then there is no foundation. Idealism does away with this foundation when it rejects the possibility of experiencing the properties of physical objects.

Berkeley questioned even more than the other empiricists. He suggested that even external reality itself may have no substance. Berkeley felt that all of our feelings and ideas can stem from our souls—just like when we are dreaming. But he also thought that all of external reality could come from another spirit. Berkeley believed that we exist only in God's mind. 

David Hume (1711-1776)

David Hume was a Scottish philosopher and modern sceptic who influenced the twentieth century movement of Logical Positivism (among others).

Hume provided a theory that explained the creation and behavior of ideas (moral philosophy versus the natural philosophy of Newton’s new discoveries in the physical sciences).  Hume divided knowledge into what he termed “relations of ideas” and “matters of fact”. Relations of ideas are analytic truths or a priori knowledge, for example, “All bachelors are unmarried” or “2 + 2 = 4”. These are certain in as much as we cannot conceive of them being otherwise. Matters of fact, however, can be falsified. To say, “The sun will rise tomorrow” is an extremely likely event, but is not impossible that it could not happen.

Hume disagreed with philosophers who held the idea that the mind contained innate ideas – Locke’s tabula rasa ("blank slate”) position. Hume was an idealist but avoided metaphysics. He was critical of the idea that we could be certain about anything outside of our experience or the true nature of the world.

Hume opposed the idea of an eternal soul. Hume was an agnostic—he felt the question of God's existence was beyond human reason. Hume believed that what we cannot know for sure that what we call laws of nature are unbreakable. Just because every time we have seen a stone dropped it has fallen to the ground does not mean that it has to do so. We simply expect it to fall. We impose our idea of cause and effect on the world. We perceive a billiard ball hitting another and decide that the first causes the movement of the second. In reality, all we have seen is that the second moves after the first and we ascribe causality to what we have seen occur again and again. Hume also pointed out that we act in accord with our feelings, not our reason. He warned against concluding that what is, is what ought to be.