a smoother-over of transitions.  It marries old opinion to new fact so as ever to show a minimum of jolt, a maximum of continuity.  We hold a theory true just in proportion to its success in solving this ‘problem of maxima and minima.’  But success in solving this problem is eminently a matter of approximation.  We say this theory solves it on the whole more satisfactorily than that theory; but that means more satisfactorily to ourselves, and individuals will emphasize their points of satisfaction differently.  To a certain degree, therefore, everything here is plastic.

The point I now urge you to observe particularly is the part played by the older truths.  Failure to take account of it is the source of much of the unjust criticism leveled against pragmatism.  Their influence is absolutely controlling.  Loyalty to them is the first principle—­in most cases it is the only principle; for by far the most usual way of handling phenomena so novel that they would make for a serious rearrangement of our preconceptions is to ignore them altogether, or to abuse those who bear witness for them.

You doubtless wish examples of this process of truth’s growth, and the only trouble is their superabundance.  The simplest case of new truth is of course the mere numerical addition of new kinds of facts, or of new single facts of old kinds, to our experience—­an addition that involves no alteration in the old beliefs.  Day follows day, and its contents are simply added.  The new contents themselves are not true, they simply come and are.  Truth is what we say about them, and when we say that they have come, truth is satisfied by the plain additive formula.

But often the day’s contents oblige a rearrangement.  If I should now utter piercing shrieks and act like a maniac on this platform, it would make many of you revise your ideas as to the probable worth of my philosophy.  ‘Radium’ came the other day as part of the day’s content, and seemed for a moment to contradict our ideas of the whole order of nature, that order having come to be identified with what is called the conservation of energy.  The mere sight of radium paying heat away indefinitely out of its own pocket seemed to violate that conservation.  What to think?  If the radiations from it were nothing but an escape of unsuspected ‘potential’ energy, pre-existent inside of the atoms, the principle of conservation would be saved.  The discovery of ‘helium’ as the radiation’s outcome, opened a way to this belief.  So Ramsay’s view is generally held to be true, because, altho it extends our old ideas of energy, it causes a minimum of alteration in their nature.