From Pius IX to John XXIII, Popes have stated that a person, to be consistent, cannot, at the same time, be a sincere Catholic and a true Socialist. To many, this attitude seems to evince sheer clerical cussedness towards positive measures intended to right economic injustices, and to dismiss the great improvements in social conditions won through the efforts of Socialists: an examination of what is meant by ‘Socialism’ in the encyclicals may accordingly dispel some misunderstandings. It should be remembered that the Church’s teaching is not an attack on all the demands of Socialists or their criticisms of Capitalism, that the meaning of the term ‘Socialist’ varies in the encyclicals depending on the circumstances of the time and that the personal attitudes of the Popes towards Socialism are reflected in the encyclicals and the timing of their publication.