Does Occam’s razor give too close a shave?

Occam’s razor is a reasonably well-known principle of methodology. The idea is to prefer parsimony to complexity, between competing hypotheses of equal explanatory power. This, intuitively, seems a sensible idea. Occam’s razor has been re-packaged and re-phrased many times, whether as the lex parsimoniae, or as Einstein’s recommendation to makes things as simple as possible, but no simpler.
All sound advice. But note, that Occam’s razor is not a law. The lex parsimoniae is only a law in the same sense that we talk of a Law of Averages; there is no actual law to speak of. Occam’s razor is more of a principle or a recommendation.
But there is a danger that this is forgotten and the negative side to the razor is overlooked. For there is a fairly obvious flaw with this idea if taken to extremes, namely the risk of rejecting an accurate, complex hypothesis in favour of a simpler hypothesis, which is also correct but less powerful.
For example, imagine Newton had proposed Einstein’s theory of general relativity instead of his mechanical, gravitational theory. Suppose he had explained general relativity precisely as Einstein had done and then had shown how in a particular, localised arrangement, the Newtonian equations of motion ‘fell out’ and that therefore he had a hypothesis for the motion of particles.
Now a devotee of Occam might suggest that a more parsimonious, yet equally powerful explanation of the simple motion of particles, is given by the Newtonian equations of motion alone. All the additional theory of relativity is completely untestable (in the late 1600s). So we should keep it simple and reject this for now. And herein lies the problem; we have just cut out a far more powerful and (presumably) accurate theory with our razor.
My point is that parsimony is desirable, but this is not a logical demand. It is a normative statement. Efficiency or simplicity we naturally covet, but we must not be beholden to them. The world is complex and a lot of the simple stuff has been explained with simple theories. But it is not unreasonable to think that more complex theories might be necessary in future, to augment our knowledge. And an over-adherence to Occam might hold us back, by its embedded potential to catapult out complex yet helpful theories.


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