General grammar was a linguistic theory which was not restricted to any particular language; its founding axiom was that sentences are the expression of subjective thought, and it began the analysis of speech by analysing the unity of the proposition. During the Eighteenth Century general grammars were conceived as empirical theories, eg theories which had to be corroborated by facts selected from natural languages. Tense theory is one of the more abstract parts of grammatical theory; the grammarians attempted to construct it by means of time parameters, the relative position of which defined each tense. For Beauzée —a cartesian rationalist— these parameters were three (the time of the event, we are speaking about, the time of the speech act, and a point of reference). For Destutt de Tracy —a condillacian sensualist— there were only two parameters; he did not need a third point of reference. The first theory was corroborated by facts of syntax (use of the same form for several time references, or without reference to the speech act, eg «aoriste», undefined); the second by morphological analogies (the french conditional was not understood as a mood, but as a future tense, and compared with the French preterit, eg «imparfait»; cf. /je serais/, «conditionnel présent»; /je serai/, «futur»; /j'étais/, «imparfait»).