Cartesian Worldview In the 16-17th centuries, many different theories were pursued. Yet, the  theories of Aristotelian-medieval mosaic were taught at the leading  universities up until the late 17th century. Question: Why did they remain accepted until the end of the 17th century?  By The 2nd Law of Scientific Change: The theories of the Aristotelian medieval mosaic remained accepted because no other theory managed to  satisfy the requirements of the method of the time. Cartesian Metaphysics: Descartes said: In order to make sure that I only accept what is true, I have to start doubting everything including my theories, my experience, the  existence of the external world, and even my own existence. But even when I doubt everything, one thing is absolutely certain: I doubt. I doubt, therefore  I think because doubting is a way of thinking. But in order to be able to doubt and think, I need to exist. Thus, the existence of my mind is beyond any  doubt. This doesn’t prove the existence of my body and the external world. Then he says, after I’ve proved my own existence (my mind), it becomes  obvious to me that God, the supremely perfecting being, exists. How can you ever prove anything like this? How can you arrive from  something like “I exist” to “God exists”? We will scrutinize Descartes’s argument for the existence of God in the next  tutorial. Question: Why would he bother proving the existence of God?  Descartes needed to prove the existence of God to prove the existence of  the material world. Descartes says: As a supremely perfect being, God is all good. Thus,  everything that I perceive clearly and distinctly, must be true. Because if it  so happened that what I perceive clearly and distinctly is not really true, it  would mean that God is a demon, a deceiver; but we know that he is all  good, therefore, he couldn’t possibly allow for such a deception to take place. Therefore, the moment you realize that a certain idea is very clear and very  distinct, you can be absolutely sure that it is true. But I perceive clearly and  distinctly that my sensations are caused by external objects. The source of  my sensations cannot be my own mind, since I have no control over them. Its not up to me to decide whether I perceive (see) a red apple or a green apple. Therefore, the source of my perceptions is something external. Thus, my  perceptions (or sensations) cannot be merely products of my imagination, because otherwise God would be deceiving me, which is impossible because  God is not a deceiver. God’s Benevolence: God is a supremely perfect being. God is all good  (benevolent).  |  V Clear/Distinct Ideas are True: Everything that I perceive clearly and  distinctly is in fact true. Descartes: I perceive clearly and distinctly that mind-independent material  world exists. Putting the above together, Descartes concludes… Matter Exists: The mind-independent material world actually exists. Descartes: What are the indispensable properties of mind and matter? I.e.  what are the properties without which these substances are inconceivable? Question: What are indispensable properties of mind?  I can’t conceive of a mind that isn’t capable of thinking, says Descartes. Mind is Thought: The principal attribute of mind is thought. Principle Attribute means essential (indispensable) property. Question: What are indispensable properties of matter?  I can’t conceive of a material object that doesn’t occupy some space, says  Descartes. Matter is Extension: The principal attribute of matter is extension (matter occupies space). Several interesting consequences follow… Dualism: There are 2 substances – extended (matter) and thinking (mind). Mechanicism: Material objects are composed of bits of interacting matter. This mechanical view has to replace Aristotelian hylomorphism. Hylomorphism: Every compound can be analytically decomposed into its  form and matter. Aristotle’s view: The human body is a compound, composed of the four  bodily fluids (described in the last lecture) and the soul, which is what makes a living thing alive. The four fluids are the matter of the body and the soul is the form of the body. Each bodily fluid is also composed of matter and form.  E.g. Blood is a compound of the four elements and the form of bloodness. Mechanicism and Hylomorphism try to answer the question: What is the  composition of matter? What is the world made of? Descartes’s view: This talk of forms is extremely occult. It gives the  impression of explanation, without actually explaining anything. In fact, once  we realize that the only attribute of matter is extension, we clearly see that  these Aristotelian forms are utterly fictitious. Descartes says that the body is essentially a complex hydraulic machine that operates purely mechanistically. Each organ is nothing but a system of  valves, pulleys, pipes, and pumps. Eventually, every effect in the body is  produced by the collisions of moving particles that compose the body. Action by Contact: Changes in material objects can result only from actual  contact. Action by contact is opposed to the Aristotelian idea of final cause. Teleology (Aristotelian view): All things tend towards certain intrinsic or  extrinsic goals. Why do animals reproduce? -> Aristotle: They reproduce because that’s their intrinsic goal. Action by Contact and Teleology are trying answer the question of: What  causes changes in material objects? Why do things move? What is the goal of human beings? Aristotle: The goal of human beings is to exercise their capacity of reason  to its best and fullest. Descartes: All this talk of goals, aims, and purposes doesn’t make any  sense, if we recall that matter has only one principal attribute – extension.  The whole idea of teleology is utter nonsense, for change can only be  brought about by actual contact. All things are mere combinations of bits of  matter in motion. Such bits can only interact by colliding with each other,  since matter doesn’t have any other capacities (such as goals). Cartesian Physiology: Changes in organisms are caused by collisions of  material particles.  |  V Changes in organisms are explicable in purely physical terms.Dualism: There are 2 substances – extended (matter) and thinking (mind).  That is all things are made of those 2 substances. This idea came to replace  the Aristotelian idea of Pluralism. Pluralism (Aristotelian): There are many types of things, each with its own substantial form. A thing is characterized by its substantial form. E.g. A  mountain is characterized by its quality of mountainness. The substantial  quality of an apple tree is its capacity to grow and bear apples. A human  being is characterized by his capacity of reason. Aristotle’s view: No matter how you rearrange the matter of the mountain,  it will never be capable of bearing fruits. Not necessarily because they are  made of different stuff. Sometimes you have two different things made of  similar stuff but they do different things because they are organized  differently. Descartes’s view: The Aristotelians multiplied substances without any  reason. In fact, there are only two substances – extended (matter) and  thinking (mind). Cartesian Dualism: All material things are nothing but systems of moving  particles. Thus, all material things are essentially different arrangements of  the same extended substance – matter. The mind, however, is a different substance. It has nothing to do with the  movement of material particles. Its primary attribute, thought, cannot be  explicated in terms of shape, size, and motion of material particles. Descartes: Therefore, human beings are the only creatures who are citizens of two different worlds – the material world and the ideal (having to do with  ideas) world. Descartes believed that there are entities which only have minds, but not  material bodies. E.g. Angels, and God. In contrast, he believed, some things are purely material (including animals). He believed animals didn’t have any capacity of thinking. Aristotelian-Medieval  Mosaic: Cartesian  Mosaic: Pluralism Dualism Teleology Action by  Contact Hylomorphism Mechanicism

Question: Why did they remain accepted until the end of the 17th century?

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Question: While pure mechanisms such as clocks seem to function through action by  contact, isn’t it the case that gravity and magnetism presuppose action at  a distance?How can Mechanicism explain gravity or magnetism? Cartesian Physics and Cosmology: The following follows from Action by Contact:  Descartes’s 1st Law: Every part of matter maintains its state unless a  collision with another part changes the state. Descartes’s 2nd Law: Every part of matter, regarded by itself, tends to  continue moving only along straight lines. Question: Can there be absolutely empty space in this mechanistic universe?  Descartes says that there can be no empty space, i.e. no space absolutely  devoid of matter. This is because space is not a separate substance, but an attribute (a property). Thus, where there is space there is matter. Plenism: There can be no empty space, i.e. no space absolutely devoid of  matter. We know that motion exists. Question: How can anything move in a plenum (a space completely filled  with matter)?  Circularity of Motion: All motion is essentially circular, i.e. it is an  interchange of positions. How would you explain gravity in Descartes’s era?  The Sun rotates around its own axis. Descartes says that this rotation creates a vortex of particles around the Sun. Gradually, the matter within the solar  vortex forms itself into a set of stratified bands, each lodging a planet, that  circle the sun at varying speeds. Some of the planets also rotate around their own axes, and thus create their own smaller vortices. The Earth’s rotation  creates a vortex of particles around the Earth. The Moon revolves around the Earth because it is in the Earth’s vortex. Since the Earth rotates around its  axis there is a centrifugal force that draws all terrestrial matter away from  the rotating Earth. Question: What would happen, if the space beyond the Earth’s vortex were  empty?  If the space beyond the Earth’s vortex were empty, all terrestrial matter  would soon disperse (fly off). But it doesn’t, says Descartes, because the  outer space is not empty. In fact, it is full of particles revolving in the solar  vortex. As a result, the finer particles (e.g. those of gases) condense at the  periphery of the terrestrial vortex. This creates an inward pressure that  pushes more rough bits of matter (e.g. solid objects) into the center of the  vortex. This inward pressure is gravity.Cartesian Gravity: Gravity is the inward pressure caused by the  condensation of finer matter at the periphery of a vortex. The mechanistic conception of gravity allowed to explain a number of both  terrestrial and celestial phenomena. E.g. The revolution of planets around  their suns and satellites (moons) around their planets. The transitions of  comets from vortex to vortex. Question: How about magnetism?  According to Descartes, the Earth is filled with parallel threaded pores that  form long passages oriented north-south. Tiny helical (corkscrew-shaped)  particles circulate from and to these threaded pores. Lodestones are also  fitted with parallel threaded pores. When reaching the lodestone, these  particles cause it to turn in the direction so that its threaded pores are  aligned with the circulating streams. This explains the orientation of the  compass towards north and south. In general, these helical particles pass  through the tiny pores of a lodestone or a piece of iron and, thus, cause  magnetic effects. Cartesian Magnetism: Magnetism is a result of the circulation of tiny  helical particles through parallel threaded pores and through space around  magnets. Hypothetico-Deductive Method: (We’ve already gone over this in  previous lectures. It is based on two principles: Complexity and Post hoc  explanations) No Experiments method (Aristotelian): (We came across this last  lecture) If a theory about the nature of a things relies in any way on  experiments, it is unacceptable. The nature is to be studied in (natural)  observations only. This is because Aristotelians believed that experiments  are unnatural because it is an artificial set up and things cannot behave in  accord with its nature in an artificial set up. Aristotelians believed in a clear  distinction between Natural vs Artificial things. There is no such clear distinction between Natural vs Artificial things in  Descartes’s theory. Descartes’s view: Since all matter is a mere combination of  extended parts, both natural and artificial things must obey the  same laws. By the theory rejection theorem, once Descartes’s theory became  accepted, the proposition from the Aristotelian era that there is a clear  distinction between Natural vs Artificial things had to go (rejected).It is replaced by… No Natural/Artificial distinction: All things obey the same laws: there is  no strict distinction between natural and artificial. Therefore, when studying the world, the artificial set up of experiments is not an obstacle. Then you arrive at the… Experimental Method: When assessing a theory, it is acceptable to rely on the results of both observations and experiments. The employment of this method (Experimental Method) legitimized  experimental science. After that, it was okay to accept the results of an  experiments just as it was okay to accept the results of (natural)  observations. Intuition vs Hypotheses Descartes: To establish the fundamental axioms, we only employ the  method of intuition. We do not need experiments to justify such fundamental principles as “matter is extension”, “the mind exists”, or “God exists”. However, explanations of specific phenomena, such as gravity or  magnetism, cannot be deduced from intuitive principles. To explain these  specific phenomena, we have to proceed hypothetically and then test our  hypotheses in experiments and observations. Qualitative vs Quantitative: Nonmathematical method (Part of the Aristotelian-Medieval  Mosaic): If a theory about certain qualitative change employs some  mathematics, it is unacceptable. It followed from the accepted theory at that  time: Mathematics: Limited Application which said that mathematics is  inapplicable to instances of qualitative change. They believed that there was  a strict distinction between qualitative vs quantitative change. Descartes’s view: This distinction between qualitative and quantitative has no place in Descartes’s theory.  Descartes says, Qualitative is Quantitative: All instances of qualitative change in material  things are essentially quantitative, for everything is only a system of moving  material particles. Any change of quality is an effect of changes in the  arrangements of underlying material particles.  |  V Thus, we arrive at another conclusion… Mathematics: Universal Application: Mathematics is applicable to all  types of change, including qualitative changes. In this world, you don’t really  have a purely qualitative change. Everything that appears to be an instance of an acquisition of a new quality is essentially a movement and  rearrangement of particles, and as such, must be explicable.   |  V Mathematical Method: Theories concerning qualitative changes are  allowed to employ mathematical tools. Any theories, really, are allowed to  employ mathematical tools. Aristotelian-Medieval  Mosaic: Cartesian Mosaic: Theories Pluralism Dualism Teleology Action by Contact Hylomorphism Mechanicism

Methods Intuitive Truth Novel Predictions No Experiments Experiments Math: Limited Application Math: Universal  Application

How can you arrive from something like “I exist” to “God exists”?

How can you ever prove anything like this?

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Tutorial: Why did the method of Novel Predictions become employed?  Because the Cartesians accepted the assumptions or the principles of  complexity and post hoc explanations was accepted.  Workshop: Goal: Evaluate the soundness and validity of an argument. An argument is valid if its conclusion logically follows from its premises. An argument is sound if it is both valid and its premises are acceptable. Thus, a logically valid argument can be either sound or unsound. But an invalid argument is always unsound. Invalid arguments can’t be  sound.

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