In his 1968 book, So Much Nearer, I.A. Richards wrote of the “Principle of Complementarity”: “This immensely important topic— publicized recently by Marshall McLuhan…”.

McLuhan wrote to Richards on July 12, 1968 (Letters 355):

I want to mention at once my gratification at your kindly reference to me on page 63 of So Much Nearer. Naturally, I owe you an enormous debt since Cambridge days.

The extent of McLuhan’s “enormous debt” may be seen in multiple posts here.

The next sentence of the letter is probably an indication that one of Richards’ books McLuhan read at Cambridge was Coleridge on Imagination:

I also owe a great deal to S.T.C.¹

McLuhan’s letter shows that he saw Richards as more than a professor and critic of English literature:

As the evolutionary process has shifted from biology to technology in the electric age, I am fascinated by your suggestion (on page three) of the possibility of a non-verbal language of macroscopic gesticulation, an interface of entire cultures. (…) Your wonderful word, ‘feedforward’, suggests to me the principle of the probe, the technique of the ‘suspended judgement’ which has been called the greatest discovery of the 20th century.²

McLuhan would see that the rigorous study of “macroscopic gesticulation” demands that its types (or elements or fundamental structures) be isolated and that this, in turn, demands free experimentation both objectively (seeing the investigated object differently) and subjectively (being the investigating subject differently³). Such free experimentation could be called the exercise of ‘feedforward’ or probing or the practice of ‘suspended judgement’.