In politics – after he left the Society of Jesus in 1634 – as a firm supporter of the «principist» party and of the House of Carignano, and in a way as its ideologist, in culture, as a theorist of the baroque concept, as a prominent dramatist and rhetorician, as historian of the Piedmontese Civil War, and finally as an educator of princes: after being tutor to Prince Thomas' children, he was tutor to Victor Amadeus II, and on that occasion wrote his Filosofia morale, which had many editions in the 18th century and, in its Russian translation, contributed Paul I's education.

[1] Tesauro is remembered chiefly for his seminal work Il cannocchiale aristotelico (The Aristotelian Telescope), the first and most important treatise on metaphor and conceit written in early modern Europe.

His father Alessandro was a noted diplomat, poet, and political figure, author of the didactic poem La sereide (1585).

This is the period in which he produced the sacred panegyrics, including his most famous example, the Giudicio (1625), and the work entitled Idea delle perfette imprese, which remained unpublished until 1975.

After leaving the order, Tesauro followed the duke's brother Thomas Francis, prince of Carignano as court historiographer during his Flemish campaign and the Piedmontese Civil War; in this period he wrote a history of the siege of Saint-Omer (Sant'Omero assediato)[9] and Campeggiamenti, overo istorie del Piemonte, first published between 1640 and 1643.

Tesauro's Filosofia morale saw twenty-seven editions over the course of the following century and translations in all of the major European languages, including French, German, Spanish, Greek, Russian and Armenian—as well as Latin (The Cambridge History of Seventeenth-Century Philosophy, 1282).

[13][14] Right from the title, Il cannocchiale aristotelico (The aristotelian telescope), Tesauro's work aims to revolutionize rhetoric and poetry in a way similar to what Galileo did in astronomy.

Tesauro defined metaphor as the "madre di tutte le argutezze" [mother of all wit],[22] whose main aim is to generate "wonder in the reader", as well as to penetrate the variety of creation.

Tesauro combines simple metaphor and allegory to propose eight further types: likeness (simiglianza), metonymy or synecdoche (attributione), punning (equivoco), hypotyposis (hipotiposi), hyperbole (hiperboli), laconism (laconismo), opposition or antithesis (oppositione), and deception (decettione).

[24] Contrary to the Spanish term agudeza, which belongs solely to literary or political discourse, wit, according to Tesauro, is not confined merely to language.

[29] Like Gracián, who believes that agudeza is our most sublime faculty, promoting us up the hierarchy of creatures, Tesauro considers wit [ingegno] "a marvelous force of the intellect,"[30] representing nothing less than the human person's direct participation in divine creative power: through the exercise of his ingegno, the artist or poet produces ex nihilo something completely new and original, in emulation of God's own initial act of creation.

[36] Inventing a metaphor is therefore an act of discovery, an exploration of the subtle network of relationships knitting all things together.Il cannocchiale aristotelico met with enormous success.

In his Entretiens d'Ariste et d'Eugène published in 1671, the Jesuit Dominique Bouhours repeatedly discusses and criticizes the ideas developed by Tesauro.

The influence of Emanuele Tesauro, Baltasar Gracián and Jakob Masen on European mannerism and the rise of the "argutia" movement is well documented in the studies by Miguel Battlori, K.-P. Lange, Wilfried Barner and Barbara Bauer.