Introduction

Two statements from the Pastoral Constitution on the Church in the Modern World (Gaudium et Spes) of the Second Vatican Council can be used together as a definition of Christian humanism. The first of these statements deals with cultural values:
...when a man applies himself to the various disciplines of philosophy, of history, and of mathematical and natural science, and when he cultivates the arts, he can do very much to elevate the human family to a more sublime understanding of truth, goodness, and beauty, and to the formation of judgments which embody universal values.[1]
The second statement deals with solidarity:
Thus we are witnesses of the birth of a new humanism, one in which man is defined first of all by his responsibility toward his brothers and toward history.[2]
The topic of Christian involvement in the world is central to the thinking of Pierre Teilhard de Chardin, the Jesuit scientist and theologian:
To incorporate the progress of the world in our picture of the kingdom of God: to incorporate the sense of the earth, the sense of man, in charity - with the world no longer eclipsing God nor carrying us away at a tangent... ‘God clothed in the world’.[3]
References:
[1] Pastoral Constitution on the Church in the Modern World” in The Documents of Vatican II, ed.Walter M. Abbott, S.J.,(New York: America Press, 1966), 263 (paragraph # 57).
[2] Ibid., 261 (paragraph # 55).
[3] Pierre Teilhard de Chardin, "The Awaited Word" in Toward the Future (New York: Harcourt Brace Jovanovich, 1975),96.

The Florentine Renaissance

The Florentine Republic
The term 'humanism' is often associated with the Italian Renaissance beginning in the fourteenth century. Today we understand that to consider this period as the rebirth of civilization after the dead "dark ages" is to be unfair to the Middle Ages, as we saw in the previous page. But nevertheless, there was an important cultural surge at this time beginning in Florence, and it played a sifnificant role in shaping what we call Christian humanism today.

As the German emperors lost effective control of Northern Italy during the thirteenth century, many of the cities in this area became self-governing republics. Florence was one of these cities. Its wealth was mostly based on a widespread network of banking and commercial activities, and a group of families effectively controlled the political system. This system resembled republican Rome, with the signoria or governing council composed mostly of members of the merchant families, taking the place of the Roman Senate.[1] Leonardo Bruni, a chancellor of Florence, celebrated the city and its renaissance:
I do enjoy the solace of living in this city, which seems by far to surpass and excel all others. It is eminent for its numerous inhabitants, its splendid buildings and its great undertakings; and in addition, some seeds of the liberal arts and of all human culture, which once seemed completely dead [an exaggeration], remained here and grow day by day and very soon, I believe, will bring forth no inconsiderable light.[2]
Humanist Circles
The man most responsible for the surge of interest in the Humanities during the fourteenth century was Francesco Petrarcha (anglicized Petrarch). Petrarch was born at Arezzo, near Florence,  in 1304, the son of a Florentine father. He started legal studies at Montpelier and Bologna, but in 1326 he abandoned these studies to dedicate himself to the pursuit of literature. While his fame grew as a poet, his study of classical poetry awakened in him a deep admiration for the civilization of Greece and specially Rome.

The sciences and the professions consist of mostly objective knowledge, but the humanities are more the result of community life, and they are better experienced in an interactive setting rather than in formal lectures. So, not surprisingly, the characteristic intellectual activity of this period was the informal gathering of friends. One of these groups gathered around the Florentine poet Bocaccio at the Augustinian monastery of Santo Spirito in Florence. Bocaccio had met Petrarch on a visit that the latter made to Florence in 1350. They immediately became friends, and as a result of this friendship, Boccacio also became interested in the classics, and he accumulated a sizable library of Latin works. Other similar groups followed this first one. Among those participating in these circles were Coluccio Salutati and Leonardo Bruni, who both became chancellors of Florence.[3]

The Humanities and Christian Values
Salutati struggled his whole life with his dual and sometimes conflicting tastes for the life of learning and for public service. In a letter to a friend who was contemplating joining a monastery, he wrote in 1398:
I grant that the contemplative life is more sublime for its high level of thought; more delectable with the sweetness of tranquility and meditation; more self sufficient since it requires fewer things; more divine since it considers divine rather than human things; more noble since it exercises the intellect,the higher part of the soul... nonetheless, the active life that you flee is to be followed both as an exercise in virtue and because of the necessity of brotherly love.[4]
Pier Paolo Vergerio, an educator influenced by Salutati, expressed the values of humanistic studies:
We call those studies liberal which are worthy of a free man; those studies by which we attain and practice virtue and wisdom; that education which calls forth, trains and develops those highest gifts of body and of mind which ennoble men, and which are rightly judged to rank next in dignity to virtue only.[5]
But “ennobling” goes beyond the practical. The study of the humanities can also help build the human spirit, a dimension that transcends performance in society. Bruni also emphasizes this aspect: "those subjects that are related to life and behavior, which are called the humanities (studia humanitatis) because they become a man, and perfect him.[6]

The cultural surge that began in Fourteenth Century Florence spread throughout Europe. Juan Luis Vives (1492-1540), a humanist that was born in Spain and taught at the University of Louvain in Belgium, emphasized the social value of knowledge:
This then the fruit of all studies; this is the goal. Having acquired our knowledge, we must turn it to usefulness, and employ it for the common good. With bold confidence, therefore, we must study all branches of knowledge for that use, for which they were appointed by God... Every study is unlimited in itself, but at some stage we ought to begin to turn it to the use and advantage of other people.[7]

References:
[1] Charles G. Nauert, Humanism and the Culture of Renaissance Europe, (Cambridge: Cambridge University Press, 1995), 13-15.
[2] Leonardo Bruni, “The Dialogues” in Gordon Griffiths, et al., eds., The Humanism of Leonardo Bruni (Binghamton, New York: State University of New York at Binghamton, 1987), 63.
[3] Charles L. Stinger, "Humanism in Florence" in Albert I. Rabil, ed., Renaissance Humanism , (University of Pennsylvania Press, 1988), 179-180.
[4] Coluccio Salutati, "Letter to Peregrino Zambeccari" in Ronald G. Witt, ed., The Earthly Republic (University of Pennsylvania Press, 1978), 111.
[5] Pier Paolo Vergerio, "De Ingenuis Moribus" in William Harrison Woodward, ed. Vittorino Da Feltre and Other Humanist Educators (Cambridge: Cambridge University Press, 1897), 102.
[6] Leonardo Bruni, "A Letter to Niccolo Strozzi" in Gordon Griffiths, et al., eds., The Humanism of Leonardo Bruni, 252.
[7]Juan Luis Vives, Vives: On Education (Cambridge: Cambridge University Press, 1913), 283-284.