The chief problem which arises when we apply our theories to any particular situation in the real world. A theory of essentially complex phenomena must refer to a large number of particular facts; and to derive a prediction from it, or to test it, we have to ascertain all these particular facts. Once we succeeded in this there should be no particular difficulty about deriving testable predictions. But there are way to many unknowable facts, and further the real danger consists in the ascertainment of the particular facts after the events have happened to comport to our theories beforehand.
Example: "OF COURSE Biden's vax mandate was all a ploy, never meant to be implemented."
You don't know that, what you're doing is taking information after events have happened and reinterpreting them to comport to your theories afterwards. You backwash your reasoning to fit current events. This way lies charlatanism and worse. Make your testable theories up PRIOR to events, or, at the very least, stick to analyzing events as they happen or after they have happened to try to ascertain what is the most objective truth.
Exactly.
A simple example will show the nature of this difficulty. Consider some ball game played by a few people of approximately equal skill. If we knew a few particular facts in addition to our general knowledge of the ability of the individual players, such as their state of attention, their perceptions and the state of their hearts, lungs, muscles etc. at each moment of the game, we could probably predict the outcome. Indeed, if we were familiar both with the game and the teams we should probably have a fairly shrewd idea on what the outcome will depend. But we shall of course not be able to ascertain those facts and in consequence the result of the game will be outside the range of the scientifically predictable, however well we may know what effects particular events would have on the result of the game.
This does not mean that we can make no predictions at all about the course of such a game. If we know the rules of the different games we shall, in watching one, very soon know which game is being played and what kinds of actions we can expect and what kind not. But our capacity to predict will be confined to such general characteristics of the events to be expected and not include the capacity of predicting particular individual events.