I answer that, There is no sin in using a thing for the purpose for which it is. Now the order of things is such that the imperfect are for the perfect, even as in the process of generation nature proceeds from imperfection to perfection.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic perfection imperfection
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Dei i, 20) : "When we hear it said, 'Thou shalt not kill,' we do not take it as referring to trees, for they have no sense, nor to irrational animals, because they have no fellowship with us. Hence it follows that the words, 'Thou shalt not kill' refer to the killing of a man."
I answer that, There is no sin in using a thing for the purpose for which it is. Now the order of things is such that the imperfect are for the perfect, even as in the process of generation nature proceeds from imperfection to perfection. Hence it is that just as in the generation of a man there is first a living thing, then an animal, and lastly a man, so too things, like the plants, which merely have life, are all alike for animals, and all animals are for man.” source