Modern physics draws from two theories: Einstein's Theory of relativity and Quantum Mechanics.
Theory of relativity states that: measurements of time and space are affected by motion between observer and what is being observed; speed of light in free space is constant and a physical boundary for motion; equivalence of mass and energy; and curvature of space-time describing the gravitational effect at every point in space.
Mean while, Quantum theory affirms: energy is radiated and absorbed in discrete "quanta"; physical quantities can change in only discrete (quanta) amounts and not in a continuous (wave-like) way; light waves act as particles and particles act like waves; more precise the position of some particle is determined, less precisely its momentum can be known and vice-versa; measuring quantum state of one particle also places constraints on the measurement of other particles.
The outcome of quantum and relativity theories has forced a re-think on the nature of physics. While classical physics depended on cause-and-effect relationship to explain phenomena, modern theories describe the physical phenomena as the result of fundamentally mathematical, indeterministic processes.
Physicists are now more inclined to say that if A occurs, there is an 'X percent' chance that B will follow. Determinism (cause-effect) in physics has been replaced by probability.
Stepping back, taking it all in, it should be evident (seen to the unseen world) that the endeavor is to find the few unifying principles that govern the behavior of nature. It is in the nature of Physics.