Physicists generally believe the laws of the Universe haven’t changed. There was an idea about a possible variable speed of light, yet that was not developed too far. One might want to throw out the word ‘eternal’ from the cosmology criterion. The Universe is believed to have had a beginning at T=0 and now is about 13.3 billion years old (unless it is an unobservable Multiverse- the boundaries could never be observed with the present physics knowledge and tech). So if it has any sort of eternal character about it that would be in one direction-outward as time and matter runs down, unless of course it is an eternally recurrent Universe that expands and contracts like a yo yo (an improbable idea and it would require constant never changing laws ad infinitum).
The reason for the assumption that the laws of physics haven’t changed since the start of the Universe is based on observations of the Universe together with the body of physics knowledge theory development and how that correlates with observations. One need distinguish between the laws of physics that exist in nature and human ideas about what those laws are. Physicists and their theories are fallible. Their ideas evolve over time and usually improve.
The Universe has a thermodynamic nature- it started highly organized and compact and unwinds to expand in a disorganized form. Initially there was just one force and field, highly compact, and it expanded and cooled down in to four primary forces that exist today. At very high temperature such as occurred at the start of the Universe the forces unify.
There is a Multiverse theory wherein each unique Universe has its own laws. Yet once the Universe starts it irreversibly flows ‘downslope’ as it were unwinding along within its particular balances of physical structure.
Physical laws are discovered rather than invented, so it is quite right that the understanding and description of physical laws may change. What does not change is the operating mechanics of any given universe. It is the operating laws of a universe that make it that particular universe.
An analogy might be that of a square box with three dimensions and six sides including the top and bottom. A box in that Universe could not have ten sides, or two sides, and be a square box. It would be possible to redefine what a side is and say for example that all of the sides of the box excluding the top and bottom are just one sides (ignoring the corners), yet the box that must exist in the Universe would be the same box regardless of how it is described (assume that there is one perfect example box that really exists to describe). In that same Universe a box described as having six sides could not be a box described as having three sides without either a logic or categorical error/inconsistency in the definition of sides.
Descartes’ Meditations about first principles of thought and certainty (epistemology) of what is known or knowable began with self-reflection on thought. Zhuangzi had a famous saying about a man dreaming he is a butterfly and vice versa- the east had several thinkers who considered the possibility that reality as illusory before Descartes. Descartes’ main differentiation from his predecessors is in his development of reason as the tool for epistemology and certainty. He wrote the Meditations of a Method while employed as a mercenary in Switzerland where he spent a lot of time inside an oven that was used as a sauna.