The real test of ‘knowledge’ is not whether it is true, but whether it empowers us.

It is a test of true theories not only to account for but to predict phenomena.

Knowledge is power. The real test of knowledge is not whether it is true but whether it empowers us. Scientists usually assume that no theory is 100% correct. Truth, consequently, is a poor test for knowledge. The real test is utility. A theory that enables us to do new things constitutes knowledge.

Relationships are the real test of whether we actually understand ourselves better.

Each piece, or part, of the whole of nature is always merely an approximation to the complete truth, or the complete truth so far as we know it. In fact, everything we know is only some kind of approximation, because we know that we do not know all the laws as yet. Therefore, things must be learned only to be unlearned again or, more likely, to be corrected. ... The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth”.

Prediction requires knowing about technologies that will be discovered in the future. But that very knowledge would almost automatically allow us to start developing those technologies right away. Ergo, we do not know what we will know.

Our test of truth is a reference to either a present or an imagined future majority in favor of our view.

Understanding reality, in the sense of being able to use what we know to predict what we don’t, is best achieved using the tools of science, and is never achieved using the methods of faith. That is attested by the acknowledged success of science in telling us about everything from the smallest bits of matter to the origin of the universe itself—compared with the abject failure of religion to tell us anything about gods, including whether they exist.

Here is the ultimate hope of saving ourselves from extinction. We must learn to understand that the contents of all knowledge is empirical; that its test is whether it works; and we must learn to act on that understanding in the world as well as in the laboratory.

The only way you’ll know the extent to which you understand reality is to put your ideas and understanding into action. If you don’t test your ideas against the real world — keep contact with the earth — how can you be sure you understand?

We do not wish to “judge” or assess out surrounding merely as a kind of expressive activity carelessly projected onto the world, but we wish to evaluate the world “correctly,” i.e., in according with that it truly is, and the desire to know is directed at determining what the world truly is.

There are those who are going to be disappointed when no life is found on other planets. Not I — I want to be reminded and delighted and surprised once again, through interplanetary exploration, with the infinite variety and novelty of phenomena that can be generated from such simple principles. The test of science is its ability to predict. Had you never visited the earth, could you predict the thunderstorms, the volcanoes, the ocean waves, the auroras, and the colorful sunset? A salutary lesson it will be when we learn of all that goes on on each of those dead planets — those eight or ten balls, each agglomerated from the same dust cloud and each obeying exactly the same laws of physics.

"So what’s the test?"
"Ah, that’s the trick of it. It’s not a test. It’s real life."

We must daily decide whether the threats we face are real, whether the solutions we are offered will do any good, whether the problems we're told exist are in fact real problems, or non-problems. Every one of us has a sense of the world, and we all know that this sense is in part given to us by what other people and society tell us; in part generated by our emotional state, which we project outward; and in part by our genuine perceptions of reality. In short, our struggle to determine what is true is the struggle to decide which of our perceptions are genuine, and which are false because they are handed down, or sold to us, or generated by our own hopes and fears.