76 THE LIFE OF SCIENCE 



plain so well a century and a half later, Leonardo actually prac- 

 ticed. 



This is, indeed, his greatest contribution: his method. He 

 deeply realized that if we are to know something of this world, 

 we can know it only by patient observation and tireless experi- 

 ment. His note-books are just full of experiments and experimental 

 suggestions, 'Try this ... do that . . ." and we find also whole 

 series of experiments, wherein one condition and then another 

 are gradually varied. Now, that may seem of little account, yet it 

 is everything. We can count on our fingers the men who devised 

 real experiments before Leonardo, and these experiments are 

 very few in number and very simple. 



But perhaps the best way to show how far he stood on the road 

 to progress, is to consider his attitude in regard to the many super- 

 stitions to which even the noblest and most emancipated minds of 

 his day paid homage, and which were to sway Europe for more 

 than two centuries after Leonardo's death. Just remember that in 

 1484, the Pope Boniface VIII had sown the seed of the witch 

 mania, and that this terrible madness was slowly incubating at the 

 time of which we are speaking. Now, Leonardo's contempt for 

 astrologers and alchemists was most outspoken and unconditional. 

 He met the spiritists of his age, as we do those of to-day, by 

 simply placing the burden of proof on their shoulders. It is true, 

 for all these matters, his Florentine ancestry stood him in good 

 stead. Petrarca had already shown how Florentine common sense 

 disposed of them; but Petrarca, man of letters, would not have 

 dared to treat* the believers in ghosts, the medical quacks, the 

 necromancers, the searchers for gold and for perpetual motion as 

 one bunch of impostors. And that is what Leonardo did repeatedly 

 and most decidedly. Oh! how they must have liked him! 



I must insist on this point: it is his ignorance which saved 

 Leonardo. I do not mean to say that he was entirely unlearned, 

 but he was sufficiently unlearned to be untrammelled. However 

 much he may have read in his mature years, I am convinced that 



