It is shown that physicists have often acted on this hypothesis in the past and that, when they have done so, progress has been made towards the unification of physics. Conclusions have, nevertheless, sometimes been based on the alternative hypothesis that the laws of physics are of the statute book kind, though perhaps inadvertently. These conclusions have later had to be abandoned in favour of non-specific ones. In this respect, it is claimed, physics differs basically from all other disciplines, including biology. The hypothesis defended here is given the name 'Principle of Minimum Assumption'. It is declared to be the most basic of all the principles of physics. If it is applied with uncompromising consistency, it precludes every ad hoc explanatory hypothesis of a specific kind. For if the Principle of Minimum Assumption holds for the whole of the physicist's universe of discourse, it must be theoretically possible to infer all other generalizations in that universe from this principle without the need for any other hypotheses.
The Hypothesis of the Symmetrical Impermanence of Matter is tested for its consistency both with what is known about causation in physics and with the conservation laws. It is shown that origins and extinctions have to be regarded as uncaused events in the same sense in which the disintegration of a radioactive atom is regarded as an uncaused event. To accept Symmetrical Impermanence is therefore not to change the physicist's present conception of the nature of causation. It is also shown that this hypothesis is not inconsistent with the conservation laws when these are given the form that expresses precisely the use to which they are put; but these laws have come often to be imprecisely worded and can then seem to refute Symmetrical Impermanence. It has to be emphasised that, according to Symmetrical Impermanence, origins and extinctions are absolute and not accompanied by the conversion of energy from one form into another. Extinctions are, therefore, not accompanied by release of any energy.
It is shown that the detailed features of the astronomical landscape are such that new clouds must form in extragalactic space at finite intervals of time and eventually acquire the characteristic shape of the spiral nebulae, including the spiral arms. One should expect the formation of these to be accompanied by turbulence in a very large quantity of very tenuous gas and to be revealed by a radio-telescope. Some of the radio-stars that have been observed in regions remote from any visible nebula may be incipient nebulae at the stage at which their spiral arms are formed.
If the new theory is true, a particle does not carry an extensive gravitational potential gradient around with it, as has hitherto been supposed. The gradient occurs only as a consequence of the extinction of the particle and as a momentary pulse. Gravitation is quantized. It could be described as the swan song of matter and not, as supposed by tradition, as its signature tune.
It is pointed out that the formation of stars from a tenuous gas and their rotation are both more difficult to explain than is often supposed. Indeed, no tenable explanation has hitherto been provided for either. It is shown that, if gravitation is quantized and the pulses in a very tenuous gas are significantly intermittent, the formation of stars as well as their rotation and the rotation of the spiral nebulae can be accounted for.
Astronomical, geological, and biological implications of this finite half-life of matter are worked out, and it is shown that it helps to explain a number of facts that have, hitherto, defied explanation. If the mass of the atomic nucleus is a region of intensely curved space, the hypothesis of a nuclear force in order to explain the cohesion of the nucleus is shown to be unnecessary. It is concluded from this that the units becoming extinct are electrons and complete atomic nuclei.