celestial movers in medieval physics 183 



St. Thomas Aquinas 



The reply of St. Thomas is the shortest and most succinct 

 of the three. He adheres strictly to the forma expected, appeal- 

 ing to the Sancti (Scripture, Augustine, Pseudo-Dionysius, 

 Gregory, Jerome) and evaluating all questions in the light of 

 Catholic faith. " It seems to me safer," he says in the prooem- 

 ium, " that doctrines commonly held by philosophers which are 

 not contrary to the faith be neither asserted as dogmas of faith 

 (although they may sometimes be introduced as philosophical 

 arguments) nor denied as contrary to the faith, lest occasion 

 be offered to men learned in human wisdom to ridicule the doc- 

 trine of faith." 



In his important theological treatise, De suhstantiis separatis, 

 St. Thomas considers the relative merits of Plato and Aristotle 

 on the question of angels.^^ Plato — really Proclus — is under- 

 stood by St. Thomas to have postulated various orders of 

 spiritual substances between the human soul and God. Under 

 God, the supreme unity and goodness, there is the order of 

 secondary gods who are the Forms or Ideas eternally radiant. 

 Inferior to these is the order of separated intellects, " which 

 participate in the above-mentioned Forms in order to have 

 actual understanding." Next come the various orders of soul, 

 each one inhabiting a certain kind of body. Celestial souls 

 animate celestial bodies and move them, in such a manner that 

 " the highest of the bodies, namely the first heaven, which is 

 moved by its own motion, receives motion from the highest 

 soul, and so on to the very lowest of the heavenly bodies." 

 Below celestial souls are the demons who inhabit unearthly 

 bodies. The lowest intellectual soul is man, who although he 

 inhabits a visible body " as a sailor in a ship," also has another 

 nobler body belonging to the soul, incorruptible and everlast- 

 ing, even as the soul itself is incorruptible. Souls below man, 

 such as plant and animal souls, lack intelligence and immor- 

 tality. If all these views of Plato were true, notes St. Thomas, 



Cap. 1-4. For the treatise De suhstantiis separatis we rely on the excellent 

 English version of Fr. Francis J. Lescoe (West Hartford: St. Joseph College, 1959) . 



