[Piers]

An example of the many ‘tricks’ the mind plays on you in order to do its job.

The brain is a decision-making organ. Its aim is to constantly make sensible decisions in situations where they matter. There is no particular reasons that the beliefs that the mind develops to help with its decision making correspond to reality, except to the extent that having accurate beliefs might improves the practical results of decision making.

If believing that water wants to go down hill makes it easier to make practically successful decisions then you mind is correct to use that belief. Similarity holding some crazy or irrational belief is no problem if it does not result in making personally harmful decisions, like deliberately flying planes into buildings.