By this statement no metaphysical pronouncement is intended.

What I mean is that we can think about nature without thinking about thought.

I shall say that then we are thinking 'homogeneously' about nature.
Of course it is possible to think of nature in conjunction with thought about the fact that nature is thought about.

In such a case I shall say that we are thinking 'heterogeneously' about nature.

In fact during the last few minutes we have been thinking heterogeneously about nature.
Natural science is exclusively concerned with homogeneous thoughts about nature.
But sense-perception has in it an element which is not thought.