A system is empirical or scientific only if it is capable of being tested by experience. These considerations suggest that not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation... It must be possible for an empirical or scientific system to be refuted by experience.

No number of sightings of white swans can prove the theory that all swans are white. The sighting of just one black one may disprove it.

The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.

Science is the century-old endeavour to bring together by means of systematic thought the perceptible phenomena of this world into as thorough-going an association as possible. To put it boldly, it is the attempt at a posterior reconstruction of existence by the process of conceptualization. Science can only ascertain what is, but not what should be, and outside of its domain value judgements of all kinds remain necessary.

Science is perhaps the only human activity in which errors are systematically criticized and, in time, corrected.

The conspiracy theory of society... comes from abandoning god and then asking: "Who is in his place"

A theory is just a mathematical model to describe the observations.