The fundamentals of physics must be rooted in measured constants and dimensional analysis.
The constants of nature are direct evidence of fundamental structure and mechanics. When constants such as Planck's constant, Bohr radius, Classical electron radius, the speed of light, Coulomb's constant, Newton's gravitational constant, and numerous other physical constants repeatedly appear in experiments and equations, then we know we are on the trail of something fundamental in physics.
Just as important as the constants themselves, are the dimensions and values of each constant. The fact that constants quantify with dimensions of mass, charge, length, and frequency tell us that these dimensions are fundamental to physics. Dimensions are properties, which are essential to the structure and mechanics of physical objects and their behaviors.
For example, the units of resistance and potential both compose from mass, charge, length and frequency, albeit the dimensions are arranged differently and with different numbers of dimensions. Resistance measures the amount of drag per length, whereas potential is a volume of electrical pressure. By changing the arrangement of dimensions we produce units, and because these units apply to quantum particles such as electrons and protons, these units are also constants.