Gilberte Pascal: The life of Pascal
Blaise Pascal's sister, Gilberte Pascal, wrote The life of Pascal which was printed in J Chevalier (ed.), Pascal, Oeuvres Complète (Libraire Gallimard, 1954). We give below some extracts from Gilberte Pascal's biography of her brother:

[My father Etienne knew] mathematics fills and satisfies the soul, [so] he did not want my brother to learn anything about it, so that he would not neglect Latin and other languages. ...
But since my father had been so careful to conceal all these [mathematical objects] from him that he did not even know their names, he ws forced to invent his own manes. Thus he called a circle a 'round' and a line a [rod], and similarly for all the rest. Using these names, he set up axioms and finally complete proofs. And since, in this matter, one proceeds from one thing to another, he continued to make progress and pushed his investigations to the point where he reached the thirtysecond proposition of Book I of Euclid [sum of the angles of a triangle is 180^{q}]. And just as he was occupied with this, my father happened to enter the room in which he was working, without my brother hearing him. He found my brother so busy that for some time he was not aware of my father's entrance. It is impossible to say who was the more surprised; the son when he saw his father and thought of the explicit prohibition the latter had uttered, or the father, when he found his son thus occupied. The astonishment of the father was even greater, however, when he asked his son whet he was doing and the latter answered that he was investigating a certain matter  which turned out to be Proposition 32 of Book I of Euclid. my father was so shocked by the greatness and ability of this genius that he left him without saying a word. ...
When Blaise Pascal was twelve years old, Etienne let him read Euclid. Gilberte Pascal describes this as follows:

He used only his hours of recreation on this study, since he was learning Latin according to the rules my father had laid down for him. Since, however, he found in this science the truth, which he had always so passionately sought, it satisfied him so completely that he threw his whole soul into the work. Thus no matter how little time he had left for it, he made such strides that at the age of sixteen he wrote a paper on the conic sections which was considered such an important intellectual achievement that it was said that nothing so powerful had been seen since Archimedes.
However Pascal gave up mathematics when he was twentyfour years old. Gilberte Pascal describes how this came about:

When he was not yet twentyfour years old, Divine Providence induced him to read pious books, and God enlightened him so much by this reading of holy works that he saw clearly that the Christian religion requires us to live only for God and to have no other goal but Him. And this truth seemed to him so enlightening, so necessary and so useful, that it put an end to all his investigations.
JOC/EFR August 2007
The URL of this page is:
http://wwwhistory.mcs.standrews.ac.uk/Pascal_life.html