All the powers of government, legislative, executive, and judiciary, result to the legislative body. The concentrating these in the same hands, is precisely the definition of despotic government. It will be no alleviation, that these powers will be exercised by a plurality of hands, and not by a single one. One hundred and seventy-three despots would surely be as oppressive as one. Let those who doubt it, turn their eyes on the republic of Venice. As little will it avail us, that they are chosen by ourselves. An elective despotism was not the government we fought for; but one which should not only be founded on free principles, but in which the powers of government should be so divided and balanced among several bodies of magistracy, as that no one could transcend their legal limits, without being effectually checked and restrained by the others. For this reason, that convention which passed the ordinance of government, laid its foundation on this basis, that the legislative, executive, and judiciary departments should be separate and distinct, so that no person should exercise the powers of more than one of them at the same time.
Source: Thomas Jefferson, Notes on the State of Virginia, P. 95.