So trading the first year of the Trump presidency tends to boil down to this: Do you think Trump can perform the miracle he's promising...? If so, then invest away! If not, then you might have another year or two left before the chickens that were hatched by the Fed in 2008 start coming home to roost.
...don't worry, everyone, the wizards of Wall Street are currently positioning themselves for one last melt-up before the whole thing goes down, so there may yet be time to squeeze another few meaningless points out of this stock market rally.
The greater fool theory states that the price of an object is determined not by its intrinsic value, but rather by irrational beliefs and expectations of market participants.