One of the most striking details to read in Iain McGilchrist's The Master and his Emissary for me, concerned the nature of the relationship between the two hemispheres of the brain. The exchange between them is essentially negative. Both can either fail to permit, by saying 'no', or permit, by not saying 'no', what the other presents to it.

The logic apparently behind this apophatic form of communication stems from the way the two hemispheres perceive the world in different ways. That difference must be preserved in order that something more than either hemisphere alone can conceive might come into being. It's not unlike Hegel's dialectic, in which the tension between a thesis and its antithesis is creative, generating a synthesis that would be impossible without the antagonism of the precursors.

Negation is, in fact, essential to being open to newness. We can only say fully 'yes' to what we already know and grasp: if you don't entirely know what you're saying 'yes' to, you are in part not saying 'no' to it. So a negative dialectic, paradoxically, has the capacity to lead us to new worlds, towards that which is beyond our comprehension, to the transcendent. It's like the sculptor whose chisel removes some wood or stone, saying 'no' to that; and who leaves some wood or stone, not saying 'no' to that. The result is a revealing of the form.

What's so fascinating about the character of this relationship between the hemispheres is that the negative way is characteristic of spiritual insight too. It's by saying God is not this or that, for this or that can only be idols - something grasped or understood - that the divine is revealed, as that which you can finally not say 'no' to. Or remember Socrates and his daimon too, the 'inner voice' that only ever said 'no' to him, telling him not to do this or that, and thereby leaving him open to new experience and the wisdom to be found at the limits of your knowledge. Or you might even recall the falsification thesis of Popper, that nothing can be proven to be true, only proven to be untrue. That which remains, that which we cannot say 'no' to, is the best approximation.

(Images: Human brain, sculptor Guy Reid)