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Spontaneous Generation


Also referred to as abiogenesis, the theory that living things arise de novo without living parents from lifeless matter, held almost universally until mid-17th century. After careful observation of the habits of animals and the life cycles of plants, aristotle concluded that some insects arise from putrefying earth or vegetable matter, oysters from slimy mud, lice from the flesh of animals, and so on. I. Newton, W. Harvey, and R. descartes were among the eminent scientists who accepted the theory without question.

The attempt of the ancients and medievals to explain the origin of lower forms of life from natural causes, rather than attributing it directly to a supramundane or divine power, was scientifically respectable. Without microscopes, these men could see neither the minute eggs of many of the invertebrates nor the spores of plants or other reproductive structures of lower animals and plants. Their scientific frame of mind demanded that they account for the change from the inanimate to the animate by proximate or proper causes; the only alternative to this, in their way of thinking, was belief in a special creation for each organism. The medievals preferred spontaneous generation for much the same reasons that 20th-century scientists seek to explain the origin of life from concatenations of molecules in the oceans of the primitive earth.

St. thomas aquinas accepted the spontaneous generation of living things from decaying matter. He also accepted the ancients' postulate that the active principle for such a power resides in some way in a celestial body. Since the sun's heat has a beneficial effect on the growth and development of living things, he thought that such heat could communicate the power of life to the slime of the earth. Not regarding the heavenly bodies as animated, however, he held that they could produce living things only in virtue of some higher power (De pot. 6.6 ad 10).

In Aquinas's terminology, the sun, not being determined to produce any one kind of animal or plant, is referred to as a universal cause (Summa theologiae 1a, 115.3 ad 3). The species of animals produced by such a cause are determined by the proportionate composition of elements in the decaying organic matter (ibid. 1a2ae, 60.1).

The forms of such organisms are not in the sun, any more than the forms of new animals or plants are in the gametes that give rise to them (ibid. 1a, 118.1 ad 4). Rather they are educed from the potency of matter, just as the form of water can be said to be educed from the potentiality of hydrogen and oxygen (see matter and form).

To avoid a disproportion between cause and effect, St. Thomas argued that just as a living canine parent must empower the seed or gamete to produce another dog, so some living being must empower a celestial body to bring forth life. In his analysis, angels could fulfill this function, since they have more knowledge of, and greater power over, celestial and terrestrial operations than man (De pot. 3.11 ad 13; 6.3). In light of man's rapidly increasing control over matter and energy, it would be in accord with such an analysis to hold that man might be able to dispose matter in such a way as to educe from it a living form. The living thing produced would then be the result of nature as well as of man's art (cf Summa theologiae. 3a, 75.6 ad 1).

See Also: life.

Bibliography: r. f. nigrelli, ed., "Modern Ideas on Spontaneous Generation," Annals of the New York Academy of Sciences 69 (1957) 257376. j. b. conant et al., eds., Harvard Case Histories in Experimental Science, 2 v. (Cambridge, MA 1957) v. 2.

[a. m. hofstetter]

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