The History and Philosophy of Astronomy Lecture 13: Descartes. Presentation

Astronomy 350L (Fall 2006)

The History and Philosophy of Astronomy (Lecture 13: Descartes)

Instructor: Volker Bromm TA: Jarrett Johnson The University of Texas at Austin

Rene Descartes: The First Modern M odern Philosopher Philosopher

• 1596

(La Haye)

– 1650 (Stockholm)

• fo foun under der of of modern modern phil philos osoph ophy y - me meth thod od of of radi radical cal dou doubt bt - mi mind nd-bo -body dy dua dualilism sm

• inv invente ented d ana analyt lytica icall geom geometry etry (Cartesian coordinates) • Im Impo porta rtanc nce e for ast astro rono nomy: my: - me mecha chanis nistic tic uni unive verse rse - in infi fini nite te uni unive vers rse e

Descartes: Timeline and Context

Descartes

• set settin ting g the intel intellect lectual ual stage stage for for Newton Newton • you younger nger cont contempo emporary rary of Galile Galileo o and Keple Keplerr

Descartes: Geography of his Life

School in La Fleche (1606-14)

• newl newly y establi established shed elit elite e school, school, run run by Jesuit Jesuits s • Curr rriiculu lum m: - Latin - sc schol holast astic ic ph philo ilosop sophy hy - stat state-of e-of-the -the-art -art math mathemat ematics ics

A Restless Early Life • 16 1615 15-- 16 16:: Uni Unive vers rsiity in Po Poit itie iers rs (l (law aw de degr gree ee)) • 161 1618: 8: joins joins Dut Dutch ch army army (as (as engin engineer) eer) • 161 1619: 9: joins joins Bava Bavarian rian army (30 Years Years War) War) • 16 162222-28: 28: lilive ves s in in Pari Paris s • Als Also: o: extens extensive ive travel travel throug throughout hout this this period period

Descartes in Paris (1622-28)

• Par Paris: is: the hots hotspot pot of the Age Age!!

Descartes in Paris: Centralization of Power

• Ca Card rdin inal al Ric Riche helilieu eu (1585-1642) - ri rise se in po powe werr - bec become omes s Chief Chief Min Minist ister er - crea creates tes cent centraliz ralized ed (abol (abolutist utistic) ic) French State - fo foun unds ds Ac Acad adem emie ie Fr Fran anca cais ise e (“guardia (“gu ardian” n” of Fren French ch langu language) age)

Descartes: A Desire for Calm and Peace • af afte terr havi having ng see seen n the the world, Descartes wants quiet time to think and write • dec decide ides s to to lea leave ve bus bustl tle e of Paris behind • mo move ve to Net Nethe herl rlan ands ds (sedentary 2nd half of his life)

Descartes in the Netherlands (1628-49)

• A young, vibrant nation: most tolerant place in Europe then!

Descartes in the Netherlands (1628-49)

• A sup super erpo powe werr of th the e 17th century!

The Dutch Golden Age (Arts and Sciences)

The Night Watch, Rembrandt (1606-69)

The Philosopher: A New System Disc scou ours rs de la la Meth Method ode  e  • Di (Discourse on the Method, 1637)

• Ra Radi dica call dou doubt bt:: - no noth thin ing g is ce certa rtain in,, but: but: - Cogito, ergo sum (I think, therefore I am)

• Du Duali alist stic ic ph phililos osoph ophy y (mind-body) • Fir First st truly truly ori origin ginal al philo philosoph sophica icall system since antiquity

The Philosopher: Radical Doubt • Des Destruc truction tion of of all previo previous us certa certainti inties es • I cannot cannot be be sure sure of what what my my senses senses tel telll me (after all, I could be dreaming…) • Bu But: t: I can canno nott dou doubt bt one thing: That I doubt (think)! • Thu Thus: s: My thin thinking king prove proves s my exist existenc ence! e! I think, therefore I am!

The Philosopher: Prove God’s Existence • I know know that that I am not not perfec perfect, t, but but I have have the the idea of a perfect being in my mind! • Thi This s perfect perfect being being can cannot not be be the same same as as me, as I myself am surely imperfect! • Thi This s perfect perfect being being would would not not be perfe perfect ct if itit did not also exist! The perfect being (God) exists!

Prove Existence of Outside Objects • In my think thinking, ing, I clearl clearly y conceiv conceive e of objects objects in the outside world! • God God,, being being perfec perfect, t, would would not not decei deceive ve me! me! The outside world exists!

• But this this outs outside ide world world is is very diff differen erentt from from the thinking mind! • The There re are are two two kinds kinds of subst substanc ance! e!

Cartesian Dualism Mind • thinks

Bodies • ha has s “e “ext xten ensi sion on”” (length, breadth, width)

• fr free ee th thou ough ght/ t/wi willll

• be beha have ve ac acco cord rdin ing g to laws of physics (determinism)

• Two realms realms of realit reality y are fundamen fundamental tally ly differe different nt and independent!

Cartesian Dualism • Th The e hum human an bo body dy is a machine • Bu Butt the the brai brain n then then is is also also part of this machine • Bi Big g Q: Q: How How do does es th the e mind interact with the brain?

Mind-Body Interaction: Clock Analogy Mind

Brain

• Min Mind d and body body only only appear appear to intera interact, ct, but but are are really pre-set in parallelism! • What about free will? (Brain follow follows s determinis deterministic tic laws…)

The Mathematician: Analytical Geometry

• me merg rge e geome geometr try y and and algeb algebra! ra! • (Ca (Cart rtes esia ian) n) Co-ord Co-ordin inat ates es!!

The Scientist: Matter in Motion • Principia Philosophiae  (Philosophical Principles, 1644)

• Theory of matter, space, and motion • A mec mecha hani nical cal sy syst stem em of the universe (matter in motion) • An in infi finit nite e un univ ivers erse e

The Scientist: Space and Matter

• beg begin in with empty empty (“undr (“undress essed”) ed”) space space of geome geometry try!!

The Scientist: Space and Matter

• Dire Direct ct coll collisi isions ons can can chang change e motion motion!!

The Scientist: Space and Matter • Th There ere can be no va vacu cuum um!! • Ass Assume ume for for the moment moment that that there there were empty empty space space!! matter Empty space

• But But:: Portion Portion of of empty empty space space has “exte “extensi nsion”! on”! • Thu Thus s (accord (according ing to Descar Descartes tes): ): There There must must also be matter (whatever has extension is matter, and vice versa!)

The Scientist: Space and Matter

• space is densely densely packed with material particl particles! es! • No gap gaps s be betw tween een!! Worl Wo rld d is a plenum !

Motion in Completely Filled Space

• partic particle le experience experiences s pushes pushes from adjacen adjacentt particle particles! s! • pat path h is bent bent into into closed closed (~ci (~circul rcular) ar) shape! shape!

Descartes Model of the Universe • vor vortex tex (whi (whirlpo rlpool) ol) cos cosmolo mology! gy! • sp spac ace/ e/mat matte terr have have no no edge! edge! • in infi fini nity ty of vo vorti rtice ces s - in infi fini nitu tude de of Su Suns ns and Solar systems • Th The e univ univer erse se has has no no cent center er and no edge!

• Re Red d pat path: h: Des Descar carte tes’ s’ (w (wron rong) g) th theor eory y for for co come mets ts!!

The Clockwork Universe

• Desca Descartes rtes establi establishes shes picture of univers universe e governed governed by simple laws of motion (the “mechanical philosophy”) • Man Many y of detailed detailed explanat explanations ions were were soon found found to be wrong, wrong, but overall overall appro approach ach became became highly influent influential ial (e.g., (e.g., Newton)! Newton)!

Toward the Infinite Universe: Thomas Digges • po popu pula lari rize zerr of Cop Coper erni nica can n mode modell (157 (1576) 6)!!

• stars ar are not confined to a thin shell!

1663: Descartes on Index of Forbidden Books Inde dex x Libroru Librorum m Pr Proh ohibi ibito torum  rum  • In

• Or Orga gani nized zed cen censo sors rshi hip p • In Intr trod oduc uced ed in 15 1559 59 • Ab Abol olis ishe hed d in in 196 1966 6

Journey’s end: Move to Stockholm • In Invi vita tati tion on fr from om Qu Queen een Christina of Sweden • De Desc scart artes es as Que Queen’ en’s s private tutor • Pr Prob oble lem: m: Des Desca cart rtes es has to show up at court already at 5am

Journey’s Journey ’s end: Death in Stockholm 1650

• contracts lethal pneumonia during fierce Swedish winter!

Descartes • Re Rene ne De Desc scar arte tes: s: - fou founde nderr of mode modern rn philos philosoph ophy y - a new new syste system m of phi philos losoph ophy y - base based d on method method of radic radical al doubt doubt (Cogito (Cogito ergo ergo sum) sum)

• Ca Cart rtes esia ian n Dua Dualilism sm - mind vs matter - Q: How How can the brain brain be influenc influenced ed by the mind/s mind/soul? oul??? ??

• Cart Cartesi esian an model model of the univ univers erse e - cons consists ists of of vortice vortices s (“matter (“matter in in motion”) motion”) - uni univer verse se is inf infini inite te - univ universe erse is govern governed ed by mecha mechanical nical laws