Why 'heresy' is now 'opinion'
In his portrait of the Reformer John Calvin, William Bouwsma makes the important observation that a fundamental shift has occurred since the sixteenth century in the philosophy of epistemology (or, how we think we know something).
A difference of opinion in the sixteenth century among theologians, like Calvin, might have led to charges of willful and dangerous heresy and punishment by death. Today such a theological difference of opinion may be allowed on the basis of the possibility of alternative interpretations.
This shift does not lie merely in the extension of a 'civilized' culture or in changes in law, or social values. It is due to a deeper move:
'Fundamental to traditional culture was a confidence that the human mind is capable of knowing what exists as it really is: as God might know it... The mind is united and becomes identical with what is known. Aristotle had said this directly: "The act of knowing is the same as the thing known."
In this conception of knowing, the role of the knower is passive: the active role in the union of knower and known is played by the object, which impresses itself on the mind.
This conception might be contrasted with the modern notion of thinking about a thing, a notion that assumes a distinction between thought and its object and recognizes the possibility of wide discrepancies between them.
The traditional conception was ... absolutist and authoritarian. If our knowledge is of things themselves as they really are, there should be, in principle, no disagreement.
Difference of opinion in matters of knowledge could only be construed as resulting from deficiency of mind or from perversity: a difference of opinion stubbornly maintained would, from this standpoint, be wicked.
In any case the truth about things, especially in important matters, must be made to prevail. This position could lead to charges of heresy not only in religion but also in the natural sciences or even history.'
John Calvin, A Sixteenth Century Portrait, pp. 69-70.