THAT is a question with a ponderously long answer! Ten seconds into it you would forget this question as other more profound heresys arise. If you are sincerely interested, I would not mind a dialogue on the subject.
I beg to disagree: Newton's laws describe reality well, but not perfectly well. And the inaccuracy happens to be greater at greater speeds.
Here we must respectfully disagree. When dealing with an exactitude (like mathematics) "not perfectly well" is not good enough. Einstein's theory (assuming it is true) is not only relevant at great speeds, but also slow speeds. It is simply that the difference between Einstein's answer to a problem involving a slow speed is indestinguishable from Newton's unless you carry the calculation out to 20 decimal places. But that difference counts.
I believe that any valid physical law must be true at ALL conditions, not just a narrow subset of conditions to be valid in general.
Especially when you're dealing in Quantum measures, where 20 decimal places is not unusual. Newtons laws were a representation of the best knowledge at the time. Einstein refined them to fit all situations.
Physics takes as postulates the following.
1. There is energy of a particle, T, associated with its motion, called kinetic.
2. There is energy of a system of particles, U, associated with interactions among them, called potential.
3. Whenever a system of particles evolves, it does so in a way that make the total vaiation of the quantity (T-U) minimal (this is Hamilton's Principle of Least Action).
Conceptually, that's it. In applications, one has to exhibit the form of the potential energy U, which is system-specific, of course. There is no empirical evidence at odds with this structure.
Which part of it qualifies as nonsense?
This is merely a difference in the semantical meaning of the words.
As far as I know, all physicists view the "truth" about reality as a limit. Very much like zero is a limit of the 1/n, that is,
1, 1/2, 1/3, 1/4, ....
The limit is zero, but no term of the sequence is zero. The truth is, similarly, the limit of our model building. No theory claims to have attained it.
Returning to the question at hand, I believe that we do agree, but have used different words to describe it. We currently beleive in the relativity theory --- just one term of the sequence, not the ultimate truth; Newton's theory departs from it more the greater the speed of the bject. In fact, Newton's theory is competely valid in the limit of speeds approaching zero -- in the sence of the limit.