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.
Action by Contact
Math: Limited Application
Math: Universal Application
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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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