We proceed to the sixth article thus:

1. Death and similar defects seem to be natural to man. It is said in 10 Metaph., text 26, that corruptibles and incorruptibles belong to different genera. But man belongs to the same genus as other animals, and they are naturally corruptible. Hence man is naturally corruptible.

2. Again, anything composed of contraries is naturally corruptible, since it contains the cause of its corruption within itself. The human body is composed of contraries. It is therefore naturally corruptible.

3. Again, the natural action of heat is to dispel humidity. Now the life of man is maintained by heat and humidity together. Since it is by the natural action of heat that his vital functions are sustained (as is said in 2 De Anima, text 50), it appears that death and similar defects are natural to man.

On the other hand: 1. God has made everything in man that is natural to him. But Wisdom 1:13 says that "God did not make death." It follows that death is not natural to man.

2. What is natural cannot be called a punishment or an evil, since what is natural is congenial. But we said in Art.5 that death and similar defects are the punishments of original sin. They cannot then be natural to man.

3. Matter is adapted to its form, and each thing is adapted to its end. Now the end of man is eternal blessedness, as we said in Q.3, Art.8, and the form of his body is his rational soul, which is incorruptible, as we said in Pt. I, Q.75, Art.6. His body is therefore naturally incorruptible.

I answer: we can speak of any corruptible thing in two ways -- according to its universal nature and according to its particular nature. The particular nature of each thing is an active and conserving power of its own, which intends both its existence and its conservation. According to this particular nature, therefore, every corruption and every defect is contrary to nature, as is said in 2 De Coelo, text 37.

The universal nature of a thing, on the other hand, is the active power of some universal principle of nature, such as one of the heavenly bodies, or some higher substance. This is the reason why God has been called Natura Naturans by some persons. Now a power of this kind intends the good and conservation of the universe, for which alternate generation and corruption in things is indispensable. According to their universal nature, therefore, the corruptions and defects of things are natural. They are not natural according to the inclination of the form of a thing, since its form is the principle of its existence and perfection. But they are natural according to the inclination of the matter which the active universal agent proportionately distributes to a form of such a kind. Each form strives to be as permanent as it can be, but no form of any corruptible thing can secure permanence for itself, with the exception of the rational soul. The rational soul is not entirely dependent on corporeal matter, as are other forms. It at least has an activity of its own which is not material, as we said in Pt. I, Q.75, Art.2, and Q.76, Art.1. Incorruption of form is therefore more natural to man than to other corruptible things. But his form is nevertheless a form whose matter is composed of contraries, and his being as a whole is consequently rendered corruptible by the inclination of its matter. According to what the nature of his material element is in itself, therefore, man is naturally corruptible. But according to the nature of his form, he is not naturally corruptible.

The first three contentions argue from the material element in man. The three which follow argue from his form. To answer them, we must observe two things. The first is that the form of man, which is his rational soul, is adapted in point of incorruptibility to his end, which is eternal blessedness. The second is that his naturally corruptible body is adapted to its form in one way, but not in another. This is because there are two kinds of condition which may be discerned in any material. There is a condition which an agent chooses, and a condition which he does not choose, but which is just the natural condition of the material itself. Thus a smith who wishes to make a knife chooses a hard and workable material, such as can be sharpened and made useful for cutting. Iron, in these respects, is a material adapted to a knife. But that it is breakable, and liable to rust, is the natural disposition of iron which the ironworker does not choose, but which he would exclude if he could. It is thus a condition adapted neither to the intention of the artisan nor to the purpose of his art. Now the human body is the material similarly chosen by nature for the sake of its moderately varied constitution, which makes it the most convenient organ of touch, and of the other sensitive and motive powers. But its corruptibility is due to the condition of matter, and nature did not choose it. Nature would rather have chosen an incorruptible material, if it could have done so. But God, to whom all nature is subject, made good this defect of nature when he created man. He bestowed a certain incorruptibility on the body by his gift of original justice, as we said in Pt. I, Q.97, Art.1. This is the reason why it is said that "God did not make death," and that death is the punishment of sin. The answers to the objections are now obvious.