- If You return to earth, come armed Lord,
because enemies are preparing other crosses
—not Turks, not Jews—but those of Your own kingdom
- "To Jesus Christ", as cited in Roush, Sherry, 2011, Selected Philosophical Poems of Tommaso Campanella, University of Chicago Press, p. 18.
- The world is the book where the eternal Wisdom wrote its own concepts
- I learn more from the anatomy of an ant or a blade of grass...than from all the books which have been written since the beginning of time. This is so, since I have begun...to read the book of God...the model according to which I correct the human books which have been copied badly and arbitrarily and without attention to the things that are written in the original book of the Universe.
- "Letter of 1607", as cited by Eisenstein, Elizabeth L., 2012, The Printing Revolution in Early Modern Europe, Cambridge University Press, p. 218.
- [A]udacious Titan of the modern age, possessing essentially a combative intellect; a poet and philosopher militant, who stood alone making war upon the authority of Aristotle in science, of Machiavelli in statecraft, and of Petrarch in art.