These are:
1. There is an external world populated by objects. The existence of those objects is independent of if the objects are perceived or not. This principle is known as objectivity. Example: there is the moon, the trees, the electrons, etc.
2. There are laws that rule the behaviour of the objects that populate the external world. Given the arbitrary initial conditions and the laws, the final conditions are established. This principle is known as determinism. For example: If the initial position and initial velocity are known at some time, besides the laws that rule the moving object, the final position and final velocity, at a posterior time, are determined.
3. There is one to one relation between the theoretical concepts and the properties of the objects. This principle is known as completeness. Example: The mass, the electric charge, etc. are concepts in theoretical classical mechanics and classical electromagnetic theory respectively; in the external world there are objects with that quantifiable properties.
4. There are relations or interrelations between the objects only at local level. This principle is known as locality. Example: An experiment performed in Mexico city does no affect the results of other experiment performed in Tokyo or in a building a few meters away from the first experiment.
5. There is a cause for every behaviour or change in the behaviour of the objects. This principle is known as causality. Example: The graphite of my pencil, which I'm using to write, got broken; the cause was the excessive pressure exerted on the pencil. Always that the pencil receives an equal pressure to the above mentioned, and in identical conditions, the graphite will get broken. The cause, as it is seen in this example, always antecede the effect.
The physicists accept tacitly the above mentioned precepts. They use them when they investigate the external world. They do it especially during the classical descriptions.
The classical description of nature, i.e., the classical theories, adjust themselves to the before mentioned precepts, the quantum theories do not; the quantum descriptions are not objective, not deterministic, not complete, not local, and not causal.