Everything produced comes into existence from non-existence; even when the substance of a thing has been in existence, and has only changed its form, the thing itself, which has gone through the process of genesis and development, and has arrived at its final state, has now different properties from those which it possessed at the commencement of the transition from potentiality to reality, or before that time. Take, e.g., the human ovum as contained in the female’s blood when still included in its vessels; its nature is different from what it was in the moment of conception, when it is met by the semen of the male and begins to develop; the properties of the semen in that moment are different from the properties of the living being after its birth when fully developed. It is therefore quite impossible to infer from the nature which a thing possesses after having passed through all stages of its development, what the condition of the thing has been in the moment when this process commenced; nor does the condition of a thing in this moment show what its previous condition has been. If you make this mistake, and attempt to prove the nature of a thing in potential existence by its properties when actually existing, you will fall into great confusion; you will reject evident truths and admit false opinions. Let us assume, in our above instance, that a man born without defect had after his birth been nursed by his mother only a few months; the mother then died, and the father alone brought him up in a lonely island, till he grew up, became wise, and acquired knowledge. Suppose this man has never seen a woman or any female being; he asks some person how man has come into existence, and how he has developed, and receives the following answer: “Man begins his existence in the womb of an individual of his own class, namely, in the womb of a female, which has a certain form. While in the womb he is very small; yet he has life, moves, receives nourishment, and gradually grows, till he arrives at a certain stage of development. He then leaves the womb and continues to grow till he is in the condition in which you see him.” The orphan will naturally ask: “Did this person, when he lived, moved, and grew in the womb, eat and drink, and breathe with his mouth and his nostrils? Did he excrete any substance?” The answer will be, “No.” Undoubtedly he will then attempt to refute the statements of that person, and to prove their impossibility, by referring to the properties of a fully developed person, in the following manner: “When any one of us is deprived of breath for a short time he dies, and cannot move any longer: how then can we imagine that any one of us has been inclosed in a bag in the midst of a body for several months and remained alive, able to move? If any one of us would swallow a living bird, the bird would die immediately when it reached the stomach, much more so when it came to the lower part of the belly; if we should not