The general influence of science at the present moment can be analysed under the headings: General Conceptions Respecting the Universe, Technological Applications, Professionalism in Knowledge, Influence of Biological Doctrines on the Motives of Conduct. I have endeavoured in the preceding lectures to give a glimpse of these points. It lies within the scope of this concluding lecture to consider the reaction of science upon some problems confronting civilised societies. The general conceptions introduced by science into modern thought cannot be separated from the philosophical situation as expressed by Descartes. I mean the assumption of bodies and minds as independent individual substances, each existing in its own right apart from any necessary reference to each other. Such a conception was very concordant with the individualism which had issued from the moral discipline of the Middle Ages. But, though the easy reception of the idea is thus explained, the derivation in itself rests upon a confusion, very natural but none the less unfortunate. The moral discipline had emphasized the intrinsic value of the individual entity. This emphasis had put the notions of the individual and of its experiences into the foreground of thought. At this point the confusion commences. The emergent individual value of each entity is transformed into the independent substantial existence of each entity, which is a very different notion. I do not mean to say that Descartes made this logical, or rather illogical, transition, in the form of explicit reasoning. Far from it. What he did, was first to concentrate upon his own conscious experiences, as being facts within the independent world of his own mentality. He was led to speculate in this way by the current emphasis upon the individual value of his total self. He implicitly transformed this emergent individual value, inherent in the very fact of his own reality, into a private world of passions, or modes, of independent substance.