Why can Congress overide a Presidential veto?

Referencing the philosophy of checks and balances in government by Montesquieu, it can be said that the power to override a Presidential veto is necessary to uphold checks and balances. Figure this: If the Congress was vastly affiliated with a specific party and planned for a bill to become an act, only to have it vetoed permanently by a polar-party President, nothing would be accomplished. Thusly, if Congress adamantly wanted to pass a bill, they could override the President's veto with 2/3 supporting consensus from both Congressional houses. (Take note that it takes 3/4 consensus from both houses to actually sent a bill to the White House for approval.)