76 EMBRYOLOGY IN ANTIQUITY [pt. ii 



final as well as efficient causes. "The ancient Nature-philosophers 

 did not see that the causes were numerous ; they only saw the material 

 and efficient causes and did not distinguish even these, while they made 

 no enquiry at all into the formal and final causes." "Democritus", 

 he says, "neglecting the final cause, reduces to Necessity all the 

 operations of Nature. Now they are necessary it is true, but yet 

 they are also for a final cause, and for the sake of what is best in 

 each case." 



Now in Aristotle this was all to the good. A metaphysician as well 

 as a scientific worker, he was able to use the concept of purposiveness 

 as a heuristic aid, but he never rested upon it. The trouble was 

 that he introduced it into the discussion at all. It is an interesting 

 speculation to consider what would have happened if the first great 

 biologist had not brought final causes into his teaching ; perhaps the 

 subsequent history of biology, and science as a whole, would have 

 been very different. For final causes irresistibly led to the theological 

 blank alleys into which men's thoughts were ushered and there left 

 to grope till the end of the Middle Ages. 



Perhaps Aristotle would not have made so many great discoveries 

 if he had been more of a Democritus. For teleology is, like other 

 varieties of common sense, useful from time to time; e.g. Harvey told 

 Boyle that he was led to certain important considerations by meditat- 

 ing upon the final cause of the valves in the veins ; and every biologist 

 acts in the same way at the present time. But the important thing 

 is not to give the last word to teleology. And those attractive shady 

 places which Aristotle, guided by his genius, quickly passed through 

 on his perpetual journeys into the hot sunlight of research and specu- 

 lation were so many traps for those who followed him. He himself 

 knew how to change rapidly from metaphysician into physicist and 

 back again, how to bow politely to the final cause and press on with 

 the dissection; but the later Peripatetics had no knowledge of this art, 

 nor had the Patristic Doctors, nor the mediaeval Aristotelians; who 

 all remained sleeping quietly in the shade of the will of God. He knew 

 very well from the sea (to use Bacon's metaphor at last) the look of 

 the Circe country of teleology, but he never visited it for long at a 

 time^ being an authentic Odysseus, unlike so many later heads, who, 

 following the example of Plato, "anchored upon that shore" and, 

 dropping their hooks to the sound of plain-song, there rode, never 

 to hoist sail again. 



