Re: John Paul II on the anthropological turn in philosophy
(The message below was sent to my mailbox, but was addressed to "everyone", so I forwarded the post to the list. : J.)
Yes, I think we can all conclude that there were multiple factors
which caused the "anthropological shift" in philosophy, not simply
Descartes meditation alone, I agree, but I think the essential point
and the point Pope John Paul II was trying to underscore, was that
this turning point, for whatever reason it DID occur (and Descartes
meditation was the catalyst for it) perpetuated all of the modern
errors of philosphy leading to extreme skepticism, the rejection of:
metaphysics, religion and faith and the rise of strict empiricsm on
one side and idealism on the other, amongst other things.
I think everyone has brought up some good points about HOW this
happened, but I think the main focus is on how this thinking
undermined catholic thought in general and JP II was proposing
a "fix" or return to, a more solid philosophical system which
acheived its height in the philosophy of Aquinas.
I think we can all agree on that?
- Regarding the history of the development of science, particularly observational astronomy and geodesy. or the study of the earth, we continue our exposition.
The foundation of geodesy as a science was established in antiquity. Aristotle and others of both Greek and Babylonian provenience proved the Earth was spherical. Next, immediately following in the space of two centuries, to this knowledge was added further astronomical speculation which led to discoveries of how the Earth is situated with respect to the Sun and stars.
Aristarchus of Samos (c. 310 - c. 230 BC) was the next Greek on the basis of observation and reason to take forward the science of astronomy inherited from Sumer/Babylonia.
Though Aristarchus' original text has been lost, Archimedes makes reference in his book The Sand Reckoner to Aristarchus' hypothesis that the Earth revolves around the Sun which is basically the same model as put forward by Copernicus 1800 years later and developed by Kepler and Newton.
"This is the common account as you have heard from astronomers. But Aristarchus has brought out a book consisting of certain hypotheses, wherein it appears, as a consequence of the assumptions made, that the universe is many times greater than the 'universe' just mentioned. His hypotheses are that the fixed stars and the Sun remain unmoved, that the Earth revolves about the Sun on the circumference of a circle..."
Louis Strong (commenting recently) says Aristarchus suspected the stars were other suns that were very far away, and that in consequence seen with the naked eye there could be no observable parallax, that is, a movement of the stars relative to each other as the Earth moves around the Sun. The stars are of course much farther away than was generally assumed in ancient times; and since stellar parallax is only detectable with telescopes, his speculation although accurate was unproveable at the time.
Along with the hypothesis of the heliocentric Earth orbit goes another hypothesis. For if the earth should revolve around the Sun, it would also necessary be that the earth revolves daily on its axis, and this daily revolution of the Earth is the physical reason why there is a sequence of night and day.
Plutarch writes that Seleucus of Seleucia gave a demonstration of Aristarchus' heliocentric model (Plutarch, Platonicae quaestiones, VIII, i). Seleucus taught sometime around 150 BC, and he is known to have been a follower of the heliocentric theory of Aristarchus of Samos, which stated that the Earth revolved around the Sun and rotated in turn around its own axis. According to Plutarch, Seleucus was the first to demonstrate the heliocentric system through reasoning, but it is not known what arguments he used.
Aristarchus also attempted to measure the relative sizes of the Earth, the Moon and the Sun.
"Some have suggested that his calculation of the relative size of the earth and sun led Aristarchus to conclude that it made more sense for the earth to be moving around the much larger sun than the other way round" (Jim (Al-Khalili, Pathfinders: The Golden Age of Arabic Science, Penguin UK, (2010), p. 270.)
Although Aristarchus' results were incorrect due to observational errors, they were based on correct geometric principles of parallax, and became the basis for estimates of the size of the Solar System for almost 2000 years, until the transit of Venus was correctly observed in 1761 and 1769. This method was proposed by Edmond Halley in 1716, although he did not live to see the results. (Measuring Venus transit times to determine solar parallax, first proposed by James Gregory in Optica Promota in regard to the transit of Mercury (in which the design of the Gregorian telescope is also described). The use of Venus transits was less successful than had been hoped due to the black drop effect, but the resulting estimate, 153 million kilometers, is just 2% above the currently accepted value, 149.6 million kilometers.
Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that generally repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years.