I have learnt that all our theories are not Truth itself, but resting places or stages on the way to the conquest of Truth, and that we must be contented to have obtained for the strivers after Truth such a resting place which, if it is on a mountain, permits us to view the provinces already won and those still to be conquered.

Liebig to Gilbert, 25 December 1870. Rothamsted Archives. Quotation supplied by W. H. Brock