 In mathematics, he published a strange treatise that arose out of his failed attempt at proving the four-colour theorem, On the Traversing of Geometrical Figures (TGF). It had virtually no echo. Farquharson quoted the mathematician E. W. Hobson explaining that Cook Wilson “hardly gave sufficient time and thought to the subject to make himself really conversant with the modern aspects of the underlying problems” (SI, xxxviii). Cook Wilson also published two short papers on probability (IP, PBT) in which he gave new proofs of the discrete Bayes’ formula and of Jacob Bernouilli’s theorem (this last being known today as the weak law of large numbers). Edgeworth called the former an “elegant proof” (Edgeworth 1911, 378, n.10), but Cook Wilson was seemingly ignorant of an already better proof of the latter via the Bienaymé-Chebyshev inequality (Seneta 2012, 448 &amp; 2013, 1104). His mathematical endeavours were otherwise largely wasted on trying to prove the inconsistency of non-Euclidean geometries. Cook Wilson claimed that he had ‘apprehended’ and thus ‘knows’ the truth of Euclid’s axiom of the parallels—he held it to be “absolutely self-evident” (SI, 561)—calling the idea of a non-Euclidean space a “chimera” (SI, 456) and non-Euclidean geometries “the mere illusion of specialists” (SI, xxxix). He thus tried in vain to find a contradiction to “convince the rank and file of mathematicians” so that “they would at least not suppose the philosophic criticism, by which I intended anyhow to attack, somehow wrong” (SI, xcvi). (See section 5 for further discussion of the point about knowledge.)