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I'm a translator, and I've run into a problem with an expression. It is an unusual expression in the original French, and while I see quite well what it means, I have no idea how to express it in English. Perhaps you can help?

The text is an academic paper concerning 17th-century history of science/philosophy. It is about the discoveries of anatomy and the success of the new anatomy in bringing down the classical Galenic conception of medicine and biology. The writer discusses the work of a 17th-century professor of anatomy, a proponent of anatomical mechanics as the sole and superior explanation for biological processes.

Here we go: the expression is "pensée en creux". "Pensée" is thought or thinking, and "creux" is a hollow or a depression. The idea expressed is of a way of thinking, an intellectual process, that reasons by subtraction. It's like identifying a silhouette not by the black image of the profile, but by the white space around it. And it is a dangerous way of thinking: even when you have seen the silhouette, you can't be sure what the person depicted actually looks like.

In this case, the writer wants to speak of the anatomist's way of thinking. The anatomist exults in the failure of Galenic conceptions of medicine (notably because of the discovery of the circulation of blood by Harvey), and by a "pensée en creux", judges that the mechanical theory is correct. Having removed the Galenic theory, all that remains in his mind is the mechanical conception, and because that is all that remains, it must be true and sufficient. That's his "pensée en creux".

Of course, this is a false dichotomy: it's not because Galenism is false that Mechanism is true.

Anyway, how might I say "pensée en creux"? It's a fairly concrete image in French, like seeing what a bronze cast must look like on the basis of seeing the hollows of the mold in which it was cast.