Difference Between Principles and Laws of Physics

The Standard Model of Particle Physics as Epistemology          

In physics there are Principles such as

1. Principle of Relativity
2. Principle of Equivalence
3. Principle of Conservation of Energy
4. Pauli Exclusion Principle 

And there are Laws such as

• Newton's Law of Gravitation
• Coulombs Law
• Gauss's Law
• Faraday's Law
• Ampère's Law
• Ohms Law 
• Hooke's Law
• Fourier's Law
• Boyle's Law
• Dalton's Law
• Ideal Gas Law
• ...

We see that there appears to be many more Laws than Principles. What in fact is the difference between a Principle and a Law of physics?

We may have an intuitive idea of a physical laws as describing a relation between physical quantities like Newton's Law of Gravitation expressing a relation between matter/mass and gravitational force, or the Ideal Gas Law expressing a relation between pressure, density and temperature in a gas. Physical laws typically involve parameters or constants as numbers such as the Gravitational constant $G$ and the gas constant $\gamma$. Laws express ontology of physical reality of what is.

But what about Principles? Inspecting the above list of Principles we meet a different situation, which rather is an expression of agreements between scientists how to view physics, that is as man-made epistemology,  Let us go through the list of Principles:

1. Principle of Relativity: Laws of physics are to have the same form in all coordinate systems.
2. Principle of Equivalence: Inertial mass is the same as gravitational mass.
3. Principle of Conservation of Energy: Energy can be transformed but total energy is constant.
4. Pauli Exclusion Principle: No two electrons with same spin can occupy the same position. 

We see no parameters and make the following observations: 

1. Principle of Relativity: Mathematical formality. Absurd or trivial. Your pick.
2. Principle of Equivalence: Agreement to relate inertial mass to gravitational mass as primordial,
3. Principle of Conservation of Energy: Agreement that nothing comes for free. Except Big Bang.
4. Pauli Exclusion Principle: Agreement to justify Standard Quantum Mechanics StdQM.

The picture seems pretty clear: Physical Laws express physics as ontology, while Principles are man-made agreements as epistemology. Another difference concerns satisfaction: A Law of Physics can be more or less true/precise as a being quantitative, while a Principle is absolute qualitative.

There are also Postulates which have the same nature as Principles. The basic Postulate of StdQM is that a physical system is described by a wave function satisfying a Schrödinger equation, which is not derived from Laws of physics. Another basic Postulate is Pauli's Exclusion Principle. 

Connecting to the previous post on StdQM, we understand that the name Pauli Exclusion Principle indicates that physicists do not view it as a law of physics to be respected by physical electrons, but rather as an agreement among physicists how to make sense of StdQM as epistemology.

On the other hand RealQM, as an alternative to StdQM, is based on Coulomb's Law for charge densities as ontology.

Recall that there is a fundamental difference between ontology of physics as what exists (without presence of humans), and epistemology as what humans say about physics. 

In classical deterministic mechanistic physics there was a clear distinction between ontology as mechanics without humans and epistemology as human observation and understanding.

Einstein's Special Theory of Relativity mixed up physics and human observation, which became manifest in StdQM with the Observer taking an even more active role through measurement deciding physics. Today the confusion is total as an expression of the crisis of modern physics. 

In Ancient Greek physics ontology and epistemology was deeply intertwined in a battle between idealism and materialism, and the Scientific Revolution had to wait for 2000 years to emerge from instead a fruitful cooperation of materialism and idealism in the form of Calculus. Today we are full swing back to idealism in the form of StdQM and String Theory.

Human Rights Principles have the form of agreements such as Universal Declaration of Human Rights adopted by UN General Assembly in 1948. Respect is not guaranteed.