As a member of the Mnemosyne (or Memory-Seekers), he spent his entire unlife searching for and translating all fragments of the Book of Nod that he could find. (His sire and grand-sire had followed the same quest before him.) This quest took him all over the world, introduced him to hundreds of different languages and cultures, and put him in contact (and conflict) with powerful vampires from all clans and sects.
Aristotle describes several of his adventures in the commentary of his edition of the Book of Nod. For example, his search for the Cycle of Lilith took him from Venice (where he encountered the Order of the Black Rose) to Boston. In Boston, he met a woman named Selina, who allowed him to continue his search after the "Dark One Herself" gave him permission to continue; he visited a bookstore run by a circle of devil-worshippers who had fragments of the text behind glass; and he encountered a mysterious Kindred woman in a graveyard, who allowed him to view a complete translation of the Cycle of Lilith from a book bound in silver, and whose power of command convinced Aristotle that she was somehow connected to the spirit-form of Lilith herself.
Believing that he would succumb to his bloodline's fatal flaw, madness brought on by thirst for knowledge, he decided to publish his English translation of the Book of Nod, which was at the time the most complete collection of Noddist lore ever assembled. Included in the publication were two forewords by Aristotle and Beckett, as well as considerable commentary on the translation by Aristotle himself. Aristotle intended to publish only about 200 copies, to be circulated only among Kindred, but the manuscript was intercepted by Ayisha Jocastian (who either received a copy from Beckett or stole it from him) and made available more widely.
Aristotle was particularly wary of the Antediluvians and those who serve them. He claimed to have learned the true name of the Brujah clan founder (presumably Troile), and woke the following evening with his own name carved into his forearm, and thereafter foreswore searching for the names of Antediluvians. Nevertheless, he remained somewhat paranoid, particularly shortly before publishing the Book of Nod. The night before writing the foreword to his text, he claimed to have seen a woman with silver-grey eyes watching him while wearing the scepter-sigil of Ventrue on her cloak. Aristotle believed that she had been sent by Ventrue himself to harry him, and this spurred him to publish sooner.