This phrase essentially refers to the glorification of man by Renaissance humanists. To a greater degree than most of their medeival predecessors, the humanists lionized the human intellect, arguing that man, as God's creation, was not debased and degraded, but capable of wonderful things. As Pico Della Mirandola put it in his Oration on the Dignity of Man:
Oh unsurpassed generosity of God the Father, Oh wondrous and unsurpassable felicity of man, to whom it is granted to have what he chooses, to be what he wills to be! The brutes, from the moment of their birth, bring with them, as Lucilius says, ``from their mother's womb'' all that they will ever possess...But upon man, at the moment of his creation, God bestowed seeds pregnant with all possibilities, the germs of every form of life.
As this passage demonstrates, the humanists, despite their "rediscovery of man," were not exactly secularists. They did not conceive of the dignity of man in terms separate from God. But it is also true that their way of thinking suffused much of the literature and the art of the day, and that many thinkers during the Renaissance sought to separate religious morality from their thought (Machiavelli, for example.)