1. Classical Empiricism The fundamental source of knowledge is sensory experience. Knowledge can be of both necessary and contingent truths. Necessary truths are still the more interesting as they tell us about the essential properties of things. There are no innate ideas. Our senses are fallible, limited and subjective. But reason is also fallible and limited. We cannot learn about the world by turning away from it. We need to investigate it empirically – scientifically. A priori knowledge of substantial truths is impossible. Only a priori knowledge of analytic truths is possible. Necessary truths are knowable a priori but only because they are trivial truths of definition.

2. EMPIRICISM – MOTIVATIONS Rationalists are “spiders”: they spin complex metaphysical systems out of their entrails. Empiricists are “bees”: they gather “pollen” (data) and works it into “honey” (knowledge). Francis Bacon (1561-1626) John Locke (1632-1704) Galileo Galilei (1564-1642) The book of nature is written in the language of mathematics. Nature is to be probed by observation and experimentation: science. Pioneering use of telescope led to discoveries that undermined Aristotle’s view of the heavens. There are no innate ideas. Knowledge is the agreement of ideas that originate in experience.

3. EMPIRICISM – LOCKEAN MOTIVATIONS There are no innate ideas. If there were innate ideas/principles, they’d be “universally assented” to. “Children, idiots and savages” are unaware of concepts such as God and cause. All ideas are either come from sensation or reflection. The simple ideas of sensation are the fundamental ideas. There are no moral rules common to every society. How could you know necessary truths such a “nothing can be both black and white” without experience of these colours? What’s the proof? John Locke (1632-1704) But even if there were things we all agreed on, this wouldn’t show they were innate. They could arise from common types of experience. E.g. we all learn the ideas of red and object and sky because we all experience these things.

4. LEIBNIZ’S REACTION TO LOCKE Our ideas are innate but not actually present in the mind. The marble has veins running through it that define a statue of Hercules. A mind is not a tabula rasa. It is like a block of marble. Gottfried Leibniz (1646-1716) By hitting the marble at its veins, the embedded statue becomes exposed. In the same way, our ideas are potentially in our minds but we need the right experiences to activate them

5. EMPIRICISM – LOCKE AND NECESSARY TRUTHS But how do we account for knowledge of necessary truths? We can’t learn that all triangles have internal angles that sum to 180 o through experience – we can’t check all of them. We learn the ideas of triangle, angle, degree and so forth from experience. Once we have these ideas, we can consider their relations to one another in our mind. We can observe that it follows from the idea of a triangle and the idea of an angle and the idea of 180 that a triangle must have internal angles that sum to 180 o So, we learn necessary truths by examining our ideas and the relationships between them. But this doesn’t solve the problem. How does our mind succeed in representing just the necessary features? You can’t say: all triangles have this property so it is necessary without having the idea of necessity… It presupposes we have the idea of necessity. How do we learn this from experience? …and you can’t say: as all triangles have property X so it is necessary property without having experienced all triangles… …and you can’t say: well, my idea of a triangle shows it to have property X on the basis of what I have seen so far, because that’s no proof it is necessary – for all we know, all the triangles you’ve seen so far might have been green.

6. EMPIRICISM – HUMEAN MOTIVATIONS All knowledge begins with impressions: the deliverances of the senses. Find me an idea that does not originate in experience. People lacking either a sensory modality (e.g. taste) or impressions (e.g. tastes of wine) cannot form ideas of these things. Our mind makes ideas: faint copies of impressions that enable us to think off-line. David Hume ((1711-1776) Proof? Impressions ‘enter with the most force and violence’ or are more ‘vivacious’ than ideas Hume’s Copy Principle: “All our simple ideas in their first appearance are derived from simple impressions, which are correspondent to them, and which they exactly represent”

7. EMPIRICISM – HUMEAN MOTIVATIONS What about necessary truths? And metaphysical concepts of God and cause and self? Matter of fact = synthetic and contingent truth. “Bernard is a bachelor” The idea of being a bachelor is no part of the idea of Bernard. It’s just a fact about Bernard that he is a bachelor. The books of metaphysics should be “consigned to the flames” Hume’s Fork: Any truth is either a “relation of ideas” or “a matter of fact” There are no substantial (interesting, metaphysical) a priori knowable truths. But what about important metaphysical truths such as “God exists”? “Every event has a cause”? Either they are mere truths of definition or they are, if true, only contingently so. Relation of ideas = analytic and necessary truth. “All bachelors are unmarried” The idea of unmarried is analytically part of the idea of a bachelor.

8. HUME AND CAUSATION Rationalists say that the concept of cause is an innate concept and that we live in a world where nothing happens without a cause. Suppose that a brick is thrown at a window and it breaks. We say that the thrown brick caused the broken window. The concept of cause is learned from experience. Furthermore, there’s no real relation of causation out there in the world. Causation is a psychological relation between impressions/ideas. But does it follow logically from the description of the first event – the thrown brick – that the second event – the broken window – would follow? No! What’s a necessary connexion? How can experience discover this? So, what does it mean to say that one thing causes another? X causes Y = (i) X and Y are spatiotemporally contiguous. (ii) X comes before Y (iii) There is a necessary connexion between cause and effect. So reason cannot discover causal connections. What’s a necessary connexion? How can experience discover this? We get the idea of a necessary connexion from seeing X-then-Y many times. So, causation boils down to the expectation that Y will follow X.

9. LOGICAL POSITIVISM The Logical Positivists were 20 th century Empiricists. The synthetic truths are the ordinary truths and the scientific truths. As Hume said, every truth is either an analytic truth or a synthetic truth. The analytic truths included not just trivial definitions but also mathematical and logical truths. At the heart of Logical Positivism is the Verification Principle: A sentence is meaningful if it can be verified (falsified) by the senses. Second, some clearly meaningful truths aren’t verifiable because they are general. For example, “all badgers are mammals” is not verifiable because we can’t check all of them. But if we find that many badgers are mammals, that is good evidence that all of them are. First, we can’t verify whether “there are badgers on Pluto” with our senses as we can’t get there. But in principle we can. But this can’t be quite right, as the Logical Positivists knew. So, we must make it: A sentence is meaningful if it can be verified in principle (falsified) by the senses or if the evidence of the senses raise make it highly probable that it is true. So, “old-fashioned” metaphysical claims such as “God exists” or “Every event has a cause” are either meaningless or contingent claims that can be scientifically verified.

10. LOGICAL POSITIVISM - PROBLEMS The verification principle, even when weakened, is flawed. Won’t the religious experiences of many people lend support to the claim that “God exists”. Swinburne’s Toy Cupboard: we can make sense of unverifiable situations. The principle is meaningless by its own standards: we cannot verify with the senses whether it is true. We believe in atoms even though we can’t seem because we have good theoretical evidence that they exists. Can’t we argue in the same way that God exists because he is the best theoretical explanation of the universe around us? Hick: the claim “there is an afterlife” passes the verification test. We will just have to wait until we die to verify it. Positivists claim that analytic sentences express necessary truths (such as the truths of maths). But there is no analytic/synthetic distinction according to Quine.

11. Quine and the Analytic/Synthetic Distinction Analytic sentences are sentences true in virtue of their meaning. Synthetic truths are sentences true in virtue of how the world is. E.g. “all metals conduct electricity” E.g. “it is sunny today” By making this distinction, the positivist can have his cake and eat it. They can allow necessary truths as simply expressing relations between concepts (rather like Locke had suggested). But how do we discover these truths? The Positivist must say, “ through reason” as she is an Empiricist But we can’t have checked all bits of metal. So, we must be making the following decision: we have evidence enough to think that all metals conduct electricity and so we’ll make it part of the definition that it does. But history shows that we often make mistakes. We might make discoveries that will require us to revise our definition of a metal as something that conducts electricity. So there is no sharp analytic/synthetic distinction. Instead, we should think of our knowledge as forming a web. So what was once held true and analytic (e.g. “water is an element) can turn out to be synthetic and false. At the centre are beliefs that are least susceptible to rejection / revision – e.g. mathematical, logical beliefs. Perhaps these can’t be rejected. Further out, we have beliefs that could be rejected/revised with less trouble: e.g. “I left my keys at home on the kitchen table this morning.” A bit further out are basic scientific beliefs. Rejecting these would cause us to have to revise much of what we believe: e.g. “badgers are animals”, “the earth is round”.