Of purpose, the phrase Christian thought has been interpreted as thought concerning Christianity. The problem which this book essays is that of an outline of the history of the thought which has been devoted, during this period of marvellous progress, to that particular object in consciousness and history which is known as Christianity. Christianity, as object of the philosophical, critical, and scientific reflection of the age--this it is which we propose to consider. Our religion as affected in its interpretation by principles of thought which are already widespread, and bid fair to become universal among educated men--this it is which in this little volume we aim to discuss. The term religious thought has not always had this significance. Philosophy of religion has signified, often, a philosophising of which religion was, so to say, the atmosphere. We cannot wonder if, in these circumstances, to the minds of some, the atmosphere has seemed to hinder clearness of vision. The whole subject of the philosophy of religion has within the last few decades undergone a revival, since it has been accepted that the aim is not to philosophise upon things in general in a religious spirit. On the contrary, the aim is to consider religion itself, with the best aid which current philosophy and science afford. In this sense only can we give the study of religion and Christianity a place among the sciences. It remains true, now as always, that the majority, at all events, of those who have thought profoundly concerning Christianity will be found to have been Christian men. Religion is a form of consciousness. It will be those who have had experience to which that consciousness corresponds, whose judgments can be supposed to have weight. That remark is true, for example, of æsthetic matters as well. To be a good judge of music one must have musical feeling and experience. To speak with any deeper reasonableness concerning faith, one must have faith. To think profoundly concerning Christianity one needs to have had the Christian experience. But this is very different from saying that to speak worthily of the Christian religion, one must needs have made his own the statements of religion which men of a former generation may have found serviceable. The distinction between religion itself, on the one hand, and the expression of religion in doctrines and rites, or the application of religion through institutions, on the other hand, is in itself one of the great achievements of the nineteenth century. It is one which separates us from Christian men in previous centuries as markedly as it does any other. It is a simple implication of the Kantian theory of knowledge. The evidence for its validity has come through the application of historical criticism to all the creeds. Mystics of all ages have seen the truth from far. The fact that we may assume the prevalence of this distinction among Christian men, and lay it at the