Q153. "A friend of a friend is trying to convince me that the United States' three branches of government was modelled on the Holy Trinity of Christianity. Is there any truth to this?"
A. No, there is no truth to it. I can, however, see how someone could come to that conclusion. First, there are three in the Trinity and three branches. To most, that's just coincidence, but if you're looking for similarities, that one is glaring. Second, in the Trinity, each part is coequal with the others; in theory, the same is true in the three branches. Third, the Trinity is said to give Christian belief stability — and the three branches have lead to a stable United States for over 200 years.
But these points are only "proof" if you see them and ignore all else.
There are many things that come in threes that it could be said the three branches are modelled upon. Three legs of a stool, for example — all equal, all providing stability. But the three branches is not based on the design of a stool, either. The fact is that the concept of three branches, legislative, executive, and judicial, was not new when presented at the Constitutional Convention. Several well-read authors, including John Locke and Montesquieu, published books many years prior to the Convention calling for such a separation of powers. The experience of the United States under the Articles of Confederation showed that a single branch was insufficient. At least some of the states had three branches of government prior to the Constitution (Vermont, for example, established a Governor and House of Representatives, and required courts be created in all counties).
In the end, the coincidence of the three in the Trinity and the three in the branches of the U.S. government is just that — coincidence.