These are four public lectures which were delivered under the auspices of the Dublin Institute for Advanced Studies at University College Dublin in February, 1950 under the title ‘Science as a Constituent of Humanism’. Neither this nor the abbreviated title chosen here adequately covers the whole, but rather the first sections only. In the remaining part, from p. 11 onward, I intend to depict the present situation in physics as it has gradually developed in the current century $ to depict it from the point of view expressed in the title and in the earlier part, thus giving, as it were, an example of how I am looking on scientific effort: as forming part of man's endeavour to grasp the human situation.

My thanks are due to the Cambridge University Press for the rapid production of this booklet and to Miss Mary Houston from the Dublin Institute for designing the figures and reading the proofs.