Praised be Jesus and Mary, now and forever.
St. Bonaventure, who has been called the second founder of the Franciscan order, was born around 1217. St. Francis was still alive at the time, and the Franciscans were in rapid expansion. Both saints were baptized with the name John, and both are known by nicknames. The name Bonaventure seems to recall the good fortune of a miraculous healing. His mother obtained from St. Francis the healing of her son from a serious illness, and St. Bonaventure would always remember that he owed his life to our Seraphic Father.
His hometown was Bagnoregio, about 70 miles north of Rome. There was a Franciscan friary there, and he probably studied with the friars. However, he did not immediately enter the Franciscan order. In 1235, when he was 17 or 18, he went to Paris to study at the university, which had the leading theological faculty in Europe. But before he could study theology, the highest branch of knowledge, he first had to master philosophy at the Faculty of Arts.
Both Franciscans and Dominicans sent their best students to the university, and both orders had the favor of the king, St. Louis IX. About a year after St. Bonaventure arrived, one of the university masters—that is, professors—became a Franciscan. This was Alexander of Hales, no minor figure, since he had introduced the custom of teaching theology by commenting on the sentences of Peter Lombard, a method that would be followed for centuries. This gave the Franciscans a teaching chair at Paris, and before the Dominicans had one, making the school of the Friars Minor an official part of the University of Paris.
St. Bonaventure eventually became very close to Alexander, whom he calls "my father and my master." Again, master here is what we would call a university professor. In 1243, St. Bonaventure followed Alexander's example by entering the Franciscans as well. Over a decade later, he explained in a letter what had led him to this decision. He wrote, "I confess before God that what made me love St. Francis' way of life so much was that it is exactly like the origin and perfection of the Church itself, which began first with simple fishermen, and afterwards developed to include the most illustrious and learned doctors. Therefore, the way of life introduced by St. Francis was proved to be God's doing when wise men did not disdain to join the company of simple folk."  What he says is an acute observation. The mission Christ gave to St. Francis is to rebuild His Church, and the method is penance, inculcated first by example and then by preaching. Franciscans reformed themselves to reform the Church, so it is not surprising that their development would resemble that of the Church. Both are modeled on Mary, the type or model of the Church. St. Bonaventure reformed himself to an astounding degree by God's grace. Alexander of Hales found St. Bonaventure to be of such innocence and dove-like simplicity that he would say that it seemed to him that Adam had never sinned in him. That is, St. Bonaventure seemed completely free from all effects of original sin, which remain in us even after baptism. Even after baptism, we have these weaknesses that we tend more easily to vice than to virtue. But in this pure soul, divine wisdom took root.
Since the Franciscan school was an official part of the university, he began his theology studies there as soon as he entered the order. He was able to study under Alexander of Hales and John of La Rochelle for two years. In 1245, both of these teachers died. St. Bonaventure continued his studies for another three years under two other Franciscans, Odo Rigaud and William of Middleton. At the same time, in 1245 to 1248, St. Thomas studied under St. Albert the Great in the Dominican school at Paris. Aquinas and Bonaventure became friends. Although one was a Franciscan and the other a Dominican, they were both from mendicant orders, both scholars and both saints.
St. Bonaventure was more cautious theologically and largely maintained the Augustinian tradition that theology had followed before him, while St. Thomas was more open to the thought of Aristotle and to remaking theology on the basis of his rediscovered philosophy. St. Bonaventure also differed in the marked Christocentrism of his theology and spirituality. In this, he is a disciple of our Seraphic Father Francis. He is known as the Seraphic Doctor for this reason and also because of the intense love that animates his teaching. No doctrine, says Jean Gerson, is "more sublime, more divine, more salutary, and more suave." Bonaventure deserves in all truth the names of Seraphim and Cherubim. He inflames the will, enlightens the intelligence, leads the soul back to God, and unites it to Him with ardent love.
Jean Gerson was Chancellor of the University of Paris a century and a half after the time of Bonaventure and Thomas. And St. Louis de Montfort calls Gerson pious and erudite and was especially impressed by his commentary on the Magnificat. Getting back to St. Bonaventure, besides his theological works, he also left us classics on the spiritual life. One day, St. Thomas asked his friend from what book he had drawn the treasures of erudition that he possessed. The Seraphic Doctor pointed to the crucifix. That was the furnace that warmed his heart and the light that illumined his intelligence with the splendors of heavenly knowledge. The Passion of Christ teaches all wisdom.
In 1248, St. Albert and St. Thomas left for Cologne, and the Seraphic Doctor took the next step in his formation at Paris. He began lecturing as a bachelor of scripture. After two years of teaching on the Bible, he was licensed as a bachelor of the sentences and lectured on dogmatic theology. Near the end of that period, St. Thomas came back to Paris and continued his own formation by lecturing as St. Bonaventure had done before him. While Aquinas was doing that in 1253 or 1254, St. Bonaventure was awarded the licentiate in doctorate, which gave him the right to teach not only in Paris but throughout Christendom.
But then a controversy broke out in the university. The Franciscans and Dominicans were being too admired by students, by the king, and becoming too influential for the taste of the secular masters of the university. They felt threatened and launched a multi-pronged attack, using their authority in the university and attacking the charisms of the Franciscans and Dominicans. Both St. Thomas and St. Bonaventure wrote in defense of the mendicant orders. The Holy See had to intervene more than once, finally ending the controversy with a definitive judgment in favor of the friars.
Meanwhile, St. Bonaventure continued to teach in the Franciscan school at Paris, and continued to teach as a master, even though the university refused to recognize him as such during the controversy. Only on August 15th, 1257, when Alexander IV ordered the university to recognize St. Thomas and St. Bonaventure as masters, did it give them their rights. St. Bonaventure had to come back for the ceremony because on February 2nd of that year, he had been elected minister general of the Franciscan order.  The order greatly needed St. Bonaventure's guidance at this time to solve internal problems and to set it on a more secure, a safer and better defined path, with better legislation and more certain spiritual guidance. He succeeded so well that he's considered the second founder of the Franciscan order.
In 1273, St. Bonaventure rose to a higher rank. Against his desires, he was created cardinal and made bishop of Albano. The pope's emissaries famously found the minister general washing dishes. He told them to hang his cardinal's hat on a tree until he finished washing. In 1274, the two holy doctors were called to Lyon, where the pope had called an ecumenical council to unite the Christians of the East and the West. St. Thomas died on his way there, leaving only St. Bonaventure. And so, Pope Gregory X presided over the council, but entrusted its work mainly to St. Bonaventure, especially the task of convincing the Greeks to accept those points necessary to end the schism. They were won over by his knowledge and his virtue and accepted everything he asked.
So, in the fourth session of the council on July 6th, they abjured the schism and recognized the primacy of the Roman pontiff. And thus, union was achieved, though it was not to last. The following day, St. Bonaventure fell ill. The mission that God had given him was complete. He had left his teaching. He had set the Franciscan order on a more solid path, and he had reunited East and West. The illness rapidly worsened, and he died on July 15th, a little over a week after the illness began. His funeral was held in the Franciscan church of the city of Lyon, with the pope and the council fathers of the East and West in attendance. A Dominican, the Cardinal of Ostia, preached the sermon, enumerating the saint's virtues.
He was canonized in 1482 by Sixtus IV and made a doctor of the Church in 1588 by Sixtus V. The latter said that St. Thomas and St. Bonaventure are like the two olive trees and the two candlesticks that enlighten the house of God, the Church, these two olive trees and candlesticks of which the Book of Revelation speaks. By a singular providence, God had raised them both up at the same time, and they are both deserving, he said, both of these Sixtuses, both deserving of the same veneration and the same honor.  
Praised be Jesus and Mary, now and forever.