Which facts are relevant and which are not relevant to a science will be relative to the current state of development of that science. - Alan Chalmers

The greater the number of conjectured theories that are confronted by the realities of the world, and the more speculative those conjectures are, the greater will be the chances of major advances in science.

It should be no news to anyone that the perceptual judgements of individuals can be unreliable for a range of reasons. The challenge, in science, is to arrange the observable situation in such a way that the reliance on such judgements is minimised if not eliminated.

The experienced and skilled observer does not have perceptual experiences identical to those of the untrained novice when the two confront the same situation.