St. Thomas on the difference between the cause of generation and terrestrial bodies

The terrestrial bodies move to a particular place, cause of generation does not.

The terrestrial bodies do not terminate all the potency of their matter, but the cause of generation does (it cannot become another, only be or not be.)

The terrestrial bodies are corruptible; the cause of generation, though bodily, is not.

The terrestrial bodies move to a particular term, the cause of generation does not, but is infinite.

The terrestrial bodies, if living, can account per se only for the generation of something like them in kind, and only as an individual; but the sun, a cause of generation, can account for the generation of many species, even as a species.

(Though St. Thomas judged that the sun was the cause of generation, most of the properties that he imutes to it can be verified of entities that are recognized, and essential to modern Physics.)


  1. February 1, 2007 at 4:49 pm

    Hip site. I was looking for Assimilatio Dei which appears to have vanished.

    Just Thomism writes : “The terrestrial bodies do not terminate all the potency of their matter”

    What is meant by ‘terminate’?

  2. a thomist said,

    February 1, 2007 at 4:59 pm

    For St. Thomas, a terrestrial body is capable of becoming something else, a cow can be eaten and become a wolf or a man. What the cow is made of, i.e. its matter, is capable of being a cow, a man, a wolf, a daisy, etc. St. Thomas held that the celetial bodies, the cause of generation, could not be anything else. He was wrong about this, but he was aware that it was a mere hypothesis, and was therefore falsifiable. It now makes more sense of the data to say that the cause of generation is the sun insofar as it is a source of electromagnetic visible waves (light) and this light, according to modern hypothesis, does not have the ability to become anything other than energy. Energy only has matter in the primary sense of matter, not in the derivative, scientific sense of “matter”.

  3. February 1, 2007 at 5:09 pm

    In which manner does substantial change not terminate all potency? What isn’t terminated?

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