Some excerpts from the book "Inventing the Individual" by Larry Siedentop

"The roots of liberalism were firmly established in the arguments of philosophers and canon lawyers by the fourteenth and early fifteenth centuries: belief in a fundamental equality of status as the proper basis for a legal system; belief that enforcing moral conduct is a contradiction in terms; a defence of individual liberty, through the assertion of fundamental or ‘natural’ rights; and, finally, the conclusion that only a representative form of government is appropriate for a society resting on the assumption of moral equality. These roots of liberalism were, however, dispersed in the fifteenth century.
(...)

If liberalism can be described as the child of Christianity, should it be called a ‘natural’ rather than a ‘legitimate’ child? There is good reason for thinking so. The reason is that liberalism as a coherent doctrine was not born willingly. It was certainly never a project of the church. Indeed, as a political theory it developed against the fierce resistance of the Catholic and even, for a long time, most Protestant churches. Its emergence was the result of a ‘civil war’ in early modern Europe, a war in which ‘liberal’ moral intuitions generated by Christianity were increasingly turned against attempts to ‘enforce’ belief. The civil war has distorted our understanding of the relationship between liberalism and Christianity. (...)

By the eighteenth century anti-clericalism had become so virulent in parts of Europe that it led to an onslaught on religious belief as such. The result was that liberal secularism in Europe came to be understood as essentially anti-religious. Its roots were interpreted in that light, with the help of the idea of the Renaissance. Any suggestion that the roots might be traced to Christianity became outlandish. (...)

That is why we have to reconsider the view that the Renaissance marked a decisive break in European history, separating a period of ignorance and superstition (the "middle ages" ) from one of freedom and progress."