Much of Engels' work is out of date judged by recent biological and other discoveries, but the essential argument respecting the interdependence of all departments of knowledge, and the impossibility of making rigid classifications holds good to-day in a wider sense than when Engels wrote. Scientific truths which have been considered absolute, theories which have produced approximately correct results, have all been discredited. The dogmas of science against which the dogmatic ecclesiastics have directed their scornful contempt have shared the same fate as the ecclesiastical dogmas. Nothing remains certain save the certainty of change. There are no ultimates. Even the atom is suspect and the claims of the elements to be elementary are rejected wholesale with something as closely resembling scorn as the scientist is ever able to attain. A scientific writer has recently said "What is undeniable is that the Daltonian atom has within a century of its acceptance as a fundamental reality suffered disruption. Its proper place in nature is not that formerly assigned to it. No longer 'in seipso totus, teres, atque rotundus' its reputation for inviolability and indestructibility is gone for ever. Each of these supposed 'ultimates' is now known to be the scene of indescribable activities, a complex piece of mechanism composed of thousands of parts, a star-cluster in miniature, subject to all kinds of dynamical vicissitudes, to perturbations, accelerations, internal friction, total or partial disruption. And to each is appointed a fixed term of existence. Sooner or later the balance of equilibrium is tilted, disturbance eventuates in overthrow; the tiny exquisite system finally breaks up. Of atoms, as of men, it may be said with truth 'Quisque suos patitur manes.'" The discovery of radium was in itself sufficient to revolutionise the heretofore existing scientific theories and the revolution thereby effected has been enough to cause Sir William Crookes to say, "There has been a vivid new start, our physicists have remodelled their views as to the constitution of matter." In his address to the physicists at Berlin the same scientist said, "This fatal quality of atomic dissociation appears to be universal, and operates whenever we brush a piece of glass with silk; it works in the sunshine and raindrops in lightnings and flame; it prevails in the waterfall and the stormy sea" and a writer in the Edinburgh Review (December, 1903) remarks in this connection "Matter he (Sir William Crookes) consequently regards as doomed to destruction. Sooner or later it will have dissolved into the 'formless mist' of protyle and 'the hour hand of eternity will have completed one revolution.' The 'dissipation of energy' has then found its correlative in the 'dissolution of Matter.'"