My apologies for a longish answer to this somewhat important question that addresses one of the challenges that faces serious students of science and philosophy today.
Let us start from the beginning. The fields of science such as physics, chemistry, biology, etc. are specialized tools of human cognition. While there is some overlap in their domains of validity, it is not always clear how these domains ought to be defined, or whether it is even advantageous to draw hard inflexible boundaries between such fields of science. For example, there is some overlap between physics and chemistry, but it is arguably wiser to leave the boundary hazy so that both physics and chemistry can coexist and grow through a synergistic relationship. Also, the separation of domains between physics and chemistry is generally not considered a source of conflict because both physics and chemistry are fundamentally based on the same language of what is known as the scientific process, therefore the playing field is essentially the same, and the players think alike as they go about their specialized profession. In contrast, the gap between philosophy and physics (and science in general) has grown wider over the past centuries, as the great natural philosophers of the past remained in the past, and scientific progress continued to march forward fueling technological development on the basis of newer scientific theories which more and more were seen to rely less on a philosophical grounding, or at least so it seemed. Consequently, the important works of philosophers of science such as Karl Popper were largely ignored, because the subject of philosophy itself was no longer held in high esteem among modern scientists, being considered more a nuisance and an obstacle to scientific advancement rather than an enabler of novel scientific ideas. Philosophy had also lost the battle in the court of public opinion before the battle was even fought. How many philosophers of science have gained in the public limelight? How many philosophers of science have there been with tangible technological achievements to showcase? Philosophy was essentially relegated to the underground. Any prominent physicist who openly admitted to deriving inspiration from natural philosophy became a physicist who was taking a big risk of being ridiculed and ostracized. Who wants to commit professional suicide?
So how does this translate to the way physics is practiced and taught in academic departments? Once the ideological fault line was drawn between philosophy and physics, translating this reality to everyday academic life became self-evident. Physics departments in general are highly conservative in terms of their zealous adherence to the currently accepted tenets and theories of physics. The academic survival of the members of the department is typically contingent on their ability to attract research funding. Imagine submitting a research proposal titled “The philosophical foundations of quantum mechanics”. One such proposal in the wrong department is enough to ruin an academic career and jeopardize the reputation of the department, so over time it is not hard to see why an academic department begins to operate like a financially motivated self-perpetuating business. Many students of physics therefore learn by example to steer away from philosophical subjects.
So, how is a serious student of physics to study the wealth of knowledge accumulated in the field of natural philosophy without risking a career? Before addressing this challenge, it seems appropriate to keep in mind that both philosophy and physics have their unique utility, but that they are different in their methodological focus. Philosophy is entirely mental, with no objective tangible means of validating its ideas, while physics deals entirely in the physical realm of nature where theories can be subjected to experimental testing and validation, and subjected to the test of prediction. But can we do any physics without mental activity? Could there be any physical law without an underlying philosophical basis? It is unthinkable. Consider Newton’s famous three laws of motion. The great scientists of the past such as Newton were deeply inspired by what we nowadays call philosophy. Unfortunately, today’s new physics is losing touch with its philosophical foundations, but is this a wise direction to pursue? Ignoring the entirety of the philosophical method in the process of developing new theories of physics is like throwing the baby out with the bathwater, even though natural philosophy is really not the baby but more the mother of physics.
Therefore, as the rift between philosophy and physics continued to widen, and as physics continued to eclipse philosophy on the stage of tangible achievements, the guiding principles as well as the checks and balances traditionally derived from philosophy also faded gradually. Physics had conquered the opposition, and was free to advance theories that were exclusively based on experimental empiricism. It seemed sufficient to ensure that any accepted theory of physics agreed with experimental data, and made the correct predictions. In time, there was nobody there to question the validity of the extrapolations that were born from an unguided interpretation of the meaning of the theories of physics. In effect, physics theories began to invent new natural philosophy. The cart was put ahead of the horse, and it seemed to matter little that the cart and horse were in a state of collective confusion.
To answer the question, the perceived conflict between philosophy and physics appears to be a conflict between practitioners of science who are focused almost entirely in their own field of specialization, and therefore have little patience (or interest) in learning more about the philosophical method that they hardly hold in high regard. To them, philosophers “philosophize”, while physicists do the real hard work of theorization, computation and experimentation, which leaves little room or incentive for collaboration. True advancement and giant leaps in science (including physics) will likely come from those pioneering scientists who bucked the trend and have been able to derive practical knowledge from beyond the boundaries of science, and that includes natural philosophy. Those who have an inadequate foundation in the basic principles of nature, as elucidated in what was known as natural philosophy, run the risk of uttering nonsense and not know that what they are claiming is fantasy more than reality, while hiding behind the false comfort of the experimental validation of their theoretical models. It is seldom emphasized that all theories of physics (and science) are only mathematical models, and not to be misused to supersede the basic principles of physical reality. One such principle is causality. If one argues that something can happen from nothingness, who is to hold the person’s feet to the fire if all the philosophers have been silenced? Some of the interpretations that defy logic in today’s fundamental physics are simply illogical, and this is where natural philosophy could have provided the mental grounding through logic. If we stray too far in our flight of fantasy, who is to stop us if all the opposition has been silenced. Natural philosophy is a rich mental field from which to choose and pick the valuable plants that can be transplanted into science. Fundamental physics that is in stark contradiction to the basic principles of physical reality may well become a confused science barking up the wrong trees.
My opinion that I would share with serious students of physics (and science) who seek to advance human knowledge through the scientific process is: if you are studying to become a physicist, by all means study natural philosophy perhaps as a hobby in your own time, and if you are a philosopher then good luck to you with studying physics on your own time because learning the methods of physics requires persistent dedication, which explains partly why physicists and philosophers find it hard to communicate constructively because they hardly speak the same language. Like our scientific pioneers, including Newton and Einstein, we have a lot to learn from observing and reflecting on the workings of nature, and what better name to call it but natural philosophy?