! Jumping ahead 2000 years:! Consider the theory of the self.! What am I? What certain knowledge do I have?! What is the relation between that knowledge and that given in the sciences?! Key figure: René Descartes.! Blackburn: modern epistemology begins on 10 November, 1619.! René Descartes (1596 1650): French mathematician, scientist and philosopher! Birth of modern science in the work of Galileo shortly before.! Physics is a mechanical science.! The world consists of physical bodies moving in space ( billiard balls ) according to deterministic laws.! Deterministic? (Problem of free will).! The everyday world is just an illusion.! First philosophy?! First science = metaphysics! But metaphysics traditionally concerned with the world (including human beings)! Descartes gives first philosophy a radically new meaning! Cogito (I think)! ergo (therefore)! sum (I am) 1
! First science for Aristotle = metaphysics! Theory that says the kinds of things there are:! There are substances (beings) with properties (material)! The substances interact causally with one another! That is: Aristotle s first science is just the most general science of what there is!! Beginning with Galileo (1564-1642), new scientific methods being developed! Gradual rejection of Aristotelian metaphysics! Galileo & Descartes believe that shape, location and size are the only material properties! There are no forms, only matter! The problem is: they are undermining Aristotle, thus Church doctrine! Metaphysics - first science - is being called into question! But: Look at the world! It doesn t look like everything is pure extended matter (colours, e.g.)! Attempt to ground radical new metaphysics calls for radical new methods! These new methods are what Descartes is calling First Philosophy! Epistemology (theory of knowledge) replaces metaphysics! What knowledge can I be certain of?! Is there an Archimedean point for knowledge?! What is the right metaphysics?! What are the fundamental metaphysical categories?! Descartes s strategy:! Doubt everything!! If you find something you cannot doubt, you ve hit bedrock! Knowledge will then have a certain foundation 2
! The demon s business:! Deceiving me about everything.! I think: I m in this room; There are other people in it (other minds); There are chairs and desks (physical objects).! Could I be deceived?! But: Could the demon deceive me into thinking that I was thinking when I wasn t?! All sensory knowledge/experience supposedly deceptive.! Not: some sensory experience (that car is red)! Not: some chunk of sensory experience (a dream)! Why not?! Because the idea that a chunk is deceptive depends on the idea that some other chunk is not deceptive.! Blackburn: forged bills.! Problem of foundations: Is absolute deceit coherent?! Objection: just because you re deceived some of the time, it doesn t follow that you re possibly deceived all of the time.! Forged bills possible only if there are real bills.! False knowledge possible only if there is real knowledge.! By contrast, possibility of the demon is possibility of absolute deceit.! If it is, how to proceed?! Every property of the wax can change, and yet we know that through all of these changes:! The wax remains, T21! Since we know this, it follows that we have some ability to think substances.! Substance: something that can exist independently of other things. (Plato s form, Aristotle s essence.)! As opposed to: a property, which depends on a substance for its existence (NB connection to ontological proof)! What s the point of these two arguments taken together?! Wax: all sensible properties (all kinds of properties) changeable.! Strict perception by the intellect alone! Demon: all sensible properties dubitable.! What is indubitable is the existence of thought, and of a thinker.! The cogito grasps the essence of that substance by the intellect alone! Descartes provides alternative first philosophy. How?! Throws the classical fundamental doctrines of metaphysics into doubt.! Replaces these with a fundamental science founded on knowledge of the self as opposed to things.! That is, he substitutes epistemology (theory of knowledge) for metaphysics (theory of things). 3
! I know that I exist. But do you?! Scientific description of other people. Here there is no Cartesian self.! Lichtenberg s objection: Why does indubitability of thought lead to indubitable existence of a thinker?! And, even if it does: To one thinker? (trans-temporal, identical)! Assume all these problems are avoidable. What does the cogito get us?! After all, what follows from this single truth?! Descartes s strategy:! Use the cogito as a basis to widen the scope of certain truth.! Cogito is clear and distinct. Hallmark of a species of truth.! Descartes: I have a clear and distinct idea of a perfect being! This idea must be caused by something more perfect.! This perfect cause must exist. Why?! Because perfect implies lacking nothing, including not lacking existence! And: God would not deceive me about clear and distinct ideas, because that would be imperfect of him.! (In)Famous Proof! Commonly known as the ontological proof of the existence of God.! Longer version: (1) All things have, in addition to their being/essence, their existence. (2) If existence is not part of their being/essence, then they depend on some other being for their existence.! Thus (3) There must be a being whose essence includes existence. (Descartes s perfect, i.e. complete, being)! But: Surely I can have ideas of things that don t exist.! Wasn t that the whole point of the Demon argument?! Descartes: Yes, but clear and distinct ideas must have a cause.! Example: Mathematics. I have clear and distinct mathematical knowledge. So! It must be about something. Triangles must exist.! Extended matter must exist.! Maybe. But Descartes needs more. He needs:! That perfection implies existence.! That God cannot deceive (perfection implies honesty).! Possible reactions?! Is the ontological proof one we should take seriously?! Should we take any *proof* of the existence of God seriously? 4
! Possible reactions?! Contra: Existence is not a predicate, and what it refers to is not a property. There is no conceptual difference between an existing horse and a possible horse.! Pro: Even if it is not a property, the existence of things as opposed to their mere possibility requires a basis/explanation/ ground.!! The existence of God?! In part. More important epistemologically:! Warrant (guarantee) for the truth of clear and distinct ideas.! We re dealing with a (potentially vicious) circle concerning metaphysics (what there is) and epistemology (what can we know).! Suppose we had complete knowledge of the nature of physical reality, including ourselves.! Then we would be able to define knowledge and truth as natural properties of the human organism.! But how can we gain complete knowledge of the nature of physical reality if we don t know what counts as knowledge and truth?! Suppose by contrast that we seek to define knowledge and truth prior to empirical knowledge of the world (a priori, like Descartes).! How could we ever be certain that the concepts we developed actually applied to reality?! Descartes s claim: We can replace the fundamental theory of what there is by a theory based on what we can know for sure.! Ultimately, we may have certain knowledge only of:! Ourselves (we are thinking things, with various faculties, e.g. memory, perception).! Mathematical physics (there are spatial things, including matter in motion).! Problem: All that could be faked by the Demon (except, perhaps, our brute existence).! Descartes can t get us outside our heads.! Indubitable not the same as true.! Example: Maybe I can t doubt that it s going to snow.! Does that warrant the claim that it will?! Rationalism: view that foundational (fundamental) truths attainable immediately, by reason.! Example: mathematics, logic, maybe bits of metaphysics, have certainty like the cogito. They are a priori (= knowable prior to experience).! Part of physics may also seem a priori.! Examples: Every event has a cause. ; Every change in motion is caused by a force. 5
! Empiricists (like David Hume) deny this.! Knowledge (mostly) purely a posteriori (posterior, subsequent to, experience).! There is foundational knowledge. But:! The foundations are not (absolutely) true or false.! Example: The fact that I always look for the cause of an event is no guarantee that there must be such a cause.! It is simply part of human nature that we think this way (useful, but not infallible).! Empiricists disagree with rationalists on the need for warranted certain foundations.! Empiricist: We learn laws & rules by experience.! Perhaps some principles are inborn: they are natural foundations. But they cannot be justified.! Rationalist: That s just complacent. I want a guarantee!! Empiricist: Every guarantee an act of faith. T42! Third option: no foundations.! All our beliefs basic, specific hang together.! Give up basic principles if specific experiences force you to.! Basic just a measure of reluctance to give them up.! Example: Mathematical truths just central to science. Not a priori, not empirical or natural either.! Asking for more than this is a delusion.! But: that doesn t mean that the knowledge we do have is not valid or justified?! Answer: It only seems that way when measured against the rationalist s concept of! One might also choose to accept the incontrovertibility of the demon argument.! Shows us that there can be no guarantee whatsoever for our foundational principles.! Nothing counts as certain knowledge.! Rational foundationalism (Descartes)! Natural foundationalism (Hume)! Coherentism! Skepticism 6