David,
Renaissance humanism was a movement beginning in the late medieval period and running through the 16th century across Europe and Britain. There were several facets to this movement.
1) The recovery and appropriation of aspects of classical culture for the renewal of Christendom;
2) Closely related to #1, the return to original literary sources made possible by the recent influx of Greek texts into the West;
3) A renewed concern for humans as such;
4) A renewal of concern for what they often termed "good letters," that is good rhetoric;
5) A renewal of concern for moral self-improvement;
6) A renewal of concern for educational reform.
The roots of the Renaissance were in the early medieval appropriation of the Trivium (grammar, logic, and rhetoric) and the Quadrivium (math, geometry, music, and astronomy). These 7 liberal arts were the educational foundation of European learning centuries before the "Renaissance" began. Nearly all theologians studied both the arts and theology and they taught both until specialization began to develop in the high medieval period (by the 13th century) and distinct university faculties began to develop in both the arts (think, "the English dept") and theology (e.g., "the Bible dept"). As tension developed between these two depts the theology dept came to be denoted as "scholastic," a practice a which the "humanistas" (those more concern with the 6 points above) excelled.
See P. O. Kristeller on the rise of humanism.
I have a chapter on the relations of the Reformation to humanism in my book on Olevian(us).
Kristeller is right when he says (as Muller says about scholasticism) that it was more a movement about method than a movement that entailed a particular philosophy.
There were Christian humanists but there were also humanists who were more attracted to ancient paganism. It was a complex movement that cannot be accurately assigned wholly to Christianity or to paganism.
Many of the 16th century Protestants were trained humanists, i.e., in the arts. Calvin combined his legal and classical studies into what has come to be called "legal humanism," wherein the the points above were applied to the study of law. Oecolampadius and Zwingli were humanists. Tyndale was influenced by humanist ideals. Melanchthon was a humanist. All these, however, also taught theology. By the 16th century, however, it's very difficult to clearly delineate in every case a "humanist" from a "scholastic." See Erica Rummel on this.
Certainly there is a distinction to be made between modern Enlightenment inspired "humanism" and the incipient humanism of the medieval church and the Renaissance. The Enlightenment asserted a sort of autonomy largely unknown prior to the modern period, but there were precursors in the Renaissance. They were, howver, a minority voice.
It is most unfortunate that some fundamentalists chose to speak of "humanism" indiscriminately as a sort of bogeyman. Such a rhetorical move reveals more about their ignorance and antipathy to learning that it does about the history of ideas or the history of the Renaissance or the nature of Enlightenment secularism.
rsc