A Euclidean theory may be claimed to be true; a quasi-empirical theory – at best – to be well-corroborated, but always conjectural. Also, in a Euclidean theory the true basic statements at the ‘top’ of the deductive system (usually called ‘axioms’) prove, as it were, the rest of the system; in a quasi-empirical theory the (true) basic statements are explained by the rest of the system. . . Mathematics is quasi-empirical
(Lakatos, 1978, pages 28-29&30)