It is very curious to find, however, that St. Thomas, in his teaching with regard to the origin and development of the human being, says, almost exactly, what the most ardent supporters of this so-called fundamental biogenetic law proclaimed in recent years. He says that "the higher a form is in the scale of being and the farther it is removed from mere material form, the more intermediate forms must be passed through before the finally perfect form is reached. Therefore, in the generation of animal and man--these having the most perfect forms--there occur many intermediate forms in generations and consequently destruction, because the generation of one being is the destruction of another." St. Thomas does not hesitate to draw his conclusions from this doctrine without hesitation. He proclaims that the human material is first animated by a vegetative soul or principle of life, and then by an animal soul and only ultimately, when the matter has {118} been properly prepared for it, by a rational soul. He said: "The vegetative soul, therefore, which is first in the embryo, while it lives the life of a plant, is destroyed, and there succeeds a more perfect soul, which is at once nutrient and sentient, and for that time the embryo lives the life of an animal: upon the destruction of this there succeeds the rational soul, infused from without." His discussion of the position of the Church and of faith to science is extremely interesting, because here once more he faces a modern problem. Aquinas was very sensitive with regard to the imposition upon Christians of things which supposedly they had to believe on the score of faith, though they were really not of faith at all. Some of his expressions in this matter are very strong and he was especially fond of quoting St. Augustine, who was very emphatic on this point. One of these typical passages deserves to find a place here because, while the word philosophy is used, it is evidently science in our modern sense of the word that is intended. Augustine talks of what the philosophers have said of the heavens or the stars and the motion of the sun and moon, meaning of course the astronomers, who were in the old days classed as natural philosophers. This passage, then, which contains the opinions of the two greatest teachers of the Church in the West may well serve as a guide for those who are interested in science, and a warning for those who would {119} obtrude faith too far into scientific questions, and thus limit investigation and hamper that freedom of intellect which is so important for the development of science. St. Thomas said in his introduction to the reply to Master John of Vercelli: