Although they are not terms often associated with Calvin (much less Calvinism!) in this day and age, John Calvin was a liberal humanist and college radical before he became known as a Protestant Reformer. His critiques of Roman Catholic theology began with (and to a large extent, are a result of) his study of the works of Jacob Faber and Desiderius Erasmus.
Jacob Faber Sepaluensis (or Jacques Lefèvre d’Étaples in French) was from the port city of Étaples, a French city very near the Dutch border. (He is identified as being from Étaples in order to distinguish him from Jacques Lefèvre Deventer, another humanist of the period from Deventer, Netherlands.) Desiderius Erasmus was from the port city of Rotterdam, Netherlands, just a few miles from Étaples.
Faber and Erasmus (and later, Calvin, while a student at the Sorbonne in Paris) were part of a radical liberal student movement in northern Europe that grew out of the Renaissance. The intent of the movement was to reform society and the Roman Catholic Church but it was perceived as dangerous and anti-Catholic by the Church. By 1533 the movement was forced underground and largely quashed in France. Although some of Faber’s and Erasmus’s books were later banned, they both remained Roman Catholic. In God’s providence, when the movement was forcibly stopped in France, rather than escaping to the Netherlands (where Faber and Erasmus were), Calvin ended up going south to Switzerland, where his philosophical and theological endeavors took a rather different turn.
In two words, the reason the “humanist” moniker fits Calvin is 1) that he took the human side of the text seriously and 2) he applied the scientific method to his study. The facet of Renaissance humanism that all three philosopher-theologians adopted was this philological method of studying written texts, including scripture. It was believed, based on a particular interpretation of Greek philosophy, that texts could be read scientifically and that authentic meaning was inherent to the texts themselves rather than to the combination of text and interpretive tradition that had grown up around the text. This new science was applied with a vengeance to scripture by John Calvin, and by the end of his life, he had written verse-by-verse commentaries on the text of scripture of all the books of the Bible except for the Apocalypse (if my memory serves me right).
It had never been a predominant Christian idea that naked texts could be accurately understood. Rather than the naked text, interpreters sought to be faithful to the normal and accepted interpretation of the text. Naked texts without contexts were too easily misconstrued because the way that humans use words is not precise. The same phrase used by the same person in different contexts could imply two very different things. Correct meaning had to be drawn from something larger than just the text.
This radically liberalizing idea that texts could be disconnected from their contexts is why the Roman Catholic Church reacted so vehemently to the student movement. Meaning became arbitrary and changeable in the Church’s view, and God’s unchangeable truth ought not to be divined from a changeable source.
What Calvin thought and wrote while a student at the Sorbonne is mostly lost, so we have to jump ahead several years to get Calvin’s response. Needless to say, the Reformers’ views of the matter were quite different. They viewed the Tradition (what the Church considered the proper context for texts to keep them from being naked) as the changeable thing, mostly human opinion. Calvin read the fathers and in his view he was reading scripture in the proper context, both by comparing scripture with scripture and comparing scripture with its social context through his reading of the Greeks and the fathers. Rather than stripping the text naked, in his view he was merely removing extraneous layers that obscured the meaning.
We have the advantage of well over 500 years of hindsight, so it is far easier for us to recognize that both sides had a point. From an Orthodox perspective (that is from a perspective that considers authentic Tradition a critical piece of understanding), medieval Roman Catholic Tradition had run off the rails by the middle ages. It had become changeable and had therefore ceased to be an authentic tool of understanding; furthermore, it had become a coercive tool of manipulation by the Church. The student radicals had good reason to be cynical about its efficacy.
But by the same token, this new scientific approach that the Dutch radicals and what would eventually become the Protestant Reformers espoused was arbitrary in its manner of how it chose to dress up the naked text. Like a teenage American girl, the Protestant sense of clothing style appropriate for the text of scripture seemed to change with the season, or at least the latest philosophical trend. Among the Continental Lutherans Romanticism was the philosophy du jour while the British Calvinists leaned toward what would become Enlightenment Rationalism. Protestant theology has always tended to be shaped the regnant philosophy of the age.
Calvin was no exception. We know that as a student he was quite fond of Seneca. It is therefore no great surprise that Calvin often read the ancient Greek texts of scripture within the broader context of Stoicism. Calvin was deeply suspicious of Seneca and it would be just as incorrect to read Stoic philosophy directly into Calvin’s theology as it would be to read Platonism directly into Orthodox theology or Aristotelianism directly into Thomistic theology. But that being said, it remains true that Calvin chose a different cultural/philosophical context for the New Testament than did the early church, and as a result his theology took a rather different trajectory than classic Christian theology.
Is Calvin’s emphasis on predestination, lack of free will, and human bondage to sin a necessary conclusion from scripture or a particular reading of a naked text subtly shaped by Stoic fatalism? The Calvinists would say it’s directly from scripture. The Roman Catholics can’t find that “radical liberal” emphasis (to continue with our theme from the Dutch Renaissance) in scripture and therefore contend that Calvin was reading Greek philosophy into scripture as a result of his new scientific emphasis at the expense of the proper cultural setting of the Bible.
So, when G.K. Chesterton claims that Calvinism took away the freedom from man, and subsequently scientific materialism bound the Creator Himself, this connection between scientific Christianity and scientific materialism is self-evident (to Chesterton). Calvinism, and especially traditional Calvinism, would argue that the Reformation didn’t take anything away from man because scripture teaches that man didn’t have any freedom in the first place, it was all an illusion. On that point, I’ll let the Catholics and the Calvinists sort it out.
What is visible in the Chesterton quote is this great divide. Chesterton, the conservative Roman Catholic, sees Protestantism as a radical liberalizing force. The Calvinists, on the other hand, tend to view Chesterton as a reactionary conservative. It’s an illustration of (to use an old canard) two ships passing in the night.