Text: Reality cannot be found except in One single source, because of the interconnection of all things with one another. ... It is a good thing to proceed in order and to establish propositions (principles). This is the way to gain ground and to progress with certainty. ... I hold that the mark of a genuine idea is that its possibility can be proved, either a priori by conceiving its cause or reason, or a posteriori when experience teaches us that it is a fact in nature. (Gottfried Leibniz, 1670)

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