Roberts, W. H. (1928). Some queries as to Kuo's doctrine of passivity. Psychological Review, 35(6), 531-532.
http://dx.doi.org/10.1037/h0070887
(See III: 528). Do not two factors, at least, enter into every chemical, physical and mechanical process, and shall we consider electrons and atoms genuine factors but deny that organisms are factors in what happens to them? (PsycINFO Database Record (c) 2016 APA, all rights reserved)