Either there are no corporeal substances, and bodies are merely phenomena which are true or consistent with each other, such as a rainbow or a perfectly coherent dream, or there is in all corporeal substances something analogous to the soul.
Gottfried LeibnizOne cannot explain words without making incursions into the sciences themselves, as is evident from dictionaries; and, conversely, one cannot present a science without at the same time defining its terms.
Gottfried LeibnizWhen a truth is necessary, the reason for it can be found by analysis, that is, by resolving it into simpler ideas and truths until the primary ones are reached. It is this way that in mathematics speculative theorems and practical canons are reduced by analysis to definitions, axioms and postulates.
Gottfried Leibniz