On the Principles of Nature

By Saint Thomas Aquinas
Translated by Roman A. Kocourek

This is a Standard Ebooks edition of St. Thomas Aquinas's philosophical treatise On the Principles of Nature, to Brother Sylvester, originally written in 1255.

The work delves into key Aristotelian-Thomistic concepts such as act and potency, matter and form, generation, and corruption, providing a foundational exploration of natural philosophy.

This edition fills a gap in available formats, as existing English PDFs were inadequate and no ePUB version existed. It is based on the excellent HTML transcription by Fr. Joseph Kenny, O.P., created in 2010 for the Dominican House of Studies in Washington, D.C., and further refined by the Aquinas Institute for their online collection at aquinas.cc.

Produced by Lucca Pellegrini using Standard Ebooks tools and style guide.
Disclaimer: I'm not a professional editor or typographer; I'm just a guy who wanted a working ePUB.
First released: November 7, 2025

Building the ePUB

To build all the ePUB files, install the Standard Ebooks toolset and run:

se build --output-dir=dist/ --kindle --kobo --check .

Contributing

If you find any issues or have suggestions for improvements, please report them on the GitHub issues page.

License

The source text and artwork in this ebook are believed to be in the United States public domain; that is, they are believed to be free of copyright restrictions in the United States. They may still be copyrighted in other countries, so users located outside of the United States must check their local laws before using this ebook. The creators of, and contributors to, this ebook dedicate their contributions to the worldwide public domain via the terms in the CC0 1.0 Universal Public Domain Dedication.