Proportionable to his capacity was his progress in literature:  at thirteen, having made himself master of school-learning, he turned his studies to philosophy and the mathematicks; and entered upon logick, under Capella, of Cremona; who, though a celebrated master of that science, confessed himself, in a very little time, unable to give his pupil further instructions.

As Capella was of the order of the Servites, his scholar was induced, by his acquaintance with him, to engage in the same profession, though his uncle and his mother represented to him the hardships and austerities of that kind of life, and advised him, with great zeal, against it.

But he was steady in his resolutions, and, in 1566, took the habit of the order, being then only in his fourteenth year, a time of life, in most persons, very improper for such engagements; but, in him, attended with such maturity of thought, and such a settled temper, that he never seemed to regret the choice he then made, and which he confirmed by a solemn publick profession, in 1572.

At a general chapter of the Servites, held at Mantua, Paul, for so we shall now call him, being then only twenty years old, distinguished himself so much, in a publick disputation, by his genius and learning, that William, duke of Mantua, a great patron of letters, solicited the consent of his superiours to retain him at his court; and not only made him publick professor of divinity in the cathedral, but honoured him with many proofs of his esteem.

But father Paul, finding a court life not agreeable to his temper, quitted it two years afterwards, and retired to his beloved privacies, being then not only acquainted with the Latin, Greek, Hebrew, and Chaldee languages, but with philosophy, the mathematicks, canon and civil law, all parts of natural philosophy, and chymistry itself; for his application was unremitted, his head clear, his apprehension quick, and his memory retentive.

Being made a priest, at twenty-two, he was distinguished by the illustrious cardinal Borromeo with his confidence, and employed by him, on many occasions, not without the envy of persons of less merit, who were so far exasperated as to lay a charge against him, before the inquisition, for denying that the trinity could be proved from the first chapter of Genesis; but the accusation was too ridiculous to be taken notice of.

After this, he passed successively through the dignities of his order, and, in the intervals of his employment, applied himself to his studies with so extensive a capacity, as left no branch of knowledge untouched.  By him Acquapendente, the great anatomist, confesses, that he was informed how vision is performed; and there are proofs, that he was not a stranger to the circulation of the blood.

He frequently conversed upon astronomy with mathematicians; upon anatomy with surgeons; upon medicine with physicians; and with chymists upon the analysis of metals, not as a superficial inquirer, but as a complete master.