In his opening lecture, James describes the methodology of his study. He explains that it would be of little benefit to base the research on common individuals who have confined religious experiences and imitate traditions which have been passed on to them. Instead, he chooses to focus the study on ‘religious geniuses’. Moreover, as he explains in his second lecture, the focus must be on personal religious experience rather than corporate, because it is more fundamental. In fact, it is out of the intense experiences of a small few that most religious movements (or ‘sects’ as he terms them) have developed. Chapter 3 establishes that people seem to have the capacity to experience the unseen and also a propensity to perceive it as being more real than things seen, heard, touched or tasted.

James argues in his fourth and fifth lectures that finding and maintaining happiness is the purpose of life. A religious experience, then, may be produced by the experience of sustained happiness. This should not be taken to mean through hedonistic living, but through attaining an inner happiness. Some people are born with an inherent optimistic outlook on life and do not generally consider the evils of the world. He terms such individuals as ‘once-born’. A belief in this optimistic mental approach to life is what motivated the ‘mind-cure’ movement influenced by Ralph Waldo Emerson and others in the United States. The fundamental premise was that a positive mental state can overcome all feelings of angst and despair and in some cases heal.

The positive mental state described in the previous lectures is contrasted in chapters 6 and 7 with the sickness of the soul which is characterised by a belief that the world is essentially evil. There are various degrees of sickness in the soul. Some are minor and may be corrected, while others are so ill as to be inhibited from experiencing joy. In the context of the framework he used in his early lectures to define the purpose of life as the pursuit and experience of joy, individuals with extremely sick souls are inhibited from attaining the fullness of life. His discussion of the sickness of the soul must be taken in the context of James’s own profound lifelong struggles with depression and melancholy. Such individuals must, James argues, experience a second birth or become ‘twice-born’ before they can experience happiness. The eighth lecture addresses how this bridge must be crossed. James suggests it stems from an internal conflict within the individual. This division must be reunified through a ‘conversion experience’. He uses Leo Tolstoy as a prime example of one restored to mental wholeness and a ‘deeper kind of conscious being than he could before’. Such an experience may take a number of forms, but in the examples of John Bunyan and St Paul, he argues it can be either a gradual process or an abrupt change. In any case, any religion that is to be of value to humanity must be able to redress the division in the mind and restore ‘healthy-mindedness’.

Conversion is the topic of lectures 9 and 10. Some conversions can change a person’s character or habits. This can occur through personal will and commitment to change. Other conversions are much more profound and alter the individual’s core being. James deduces that such a deep change in a person might imply an external impetus of change and is often accompanied by a sense of the Other and the revelation of new truths. However, not all conversions can be attributed to the intervention of an external Other.

In lectures 11–15, James addresses the change conversion can instil in the form of saintly living brought about by a belief in the transcendent and a sense of a profound significance in life. He refers to the outcome of saintly living as ‘practical fruits’: belief in a wider life beyond selfish interest; continuity with and a willingness to surrender to ‘the ideal power’; an immense sense of elation and freedom; shift of the emotional sense towards loving affections. A sense of profound purpose can be manifested in one of two ways. One is an exuberance of joy and a sense of liberty, as exhibited in George Fox and the Quaker movement, while the other is solemn submission to the will of the Divine. Asceticism is another aspect of saintly living, in which the subject finds happiness through self-denial and withdrawal from the distractions of society. The danger of asceticism is in it being taken to extremes which view the needs of the body as wholly detrimental. James deems this to be a neurosis and cites St John of the Cross as an example. Saintly living can in some cases lead to fanaticism and belligerent personas or to a profound gentleness of spirit. The latter James terms ‘theopathic saintliness’ and lauds such personalities as visionaries.

In lectures 16 and 17, the concept of mysticism is addressed. By its nature as a personal occurrence, mystical experience cannot be defined in an absolute and universal way, although there are some general attributes. The experience is not usually predictable and as such might be defined as ephemeral in nature. The experience is often described by the subject as losing a sense of the self and being overcome by the Other. The subject of a mystical experience is left feeling a heightened insight or knowledge. In this sense, it is ‘noetic’ and rooted in the mind.

The final three lectures may be viewed as summary. Lecture 18 explains the inability of philosophy to explain religious experience because by its nature it is beyond logical constructs or appraisal and it cannot be adequately described in conceptual or linguistic terms: ‘I do believe that feeling is the deeper source of religion, and that philosophic and theological formulas are secondary products’. He suggests that the role of science of religion is to help fill the void left by philosophy’s insufficiency in defining religious experience. Lecture 19, aptly titled ‘Other Characteristics’, deals with a wide variety of subject matter, including institutional religion, prayer and the relationship between religion and the subconscious. In terms of organized religion, James states that room must be given for personal religious experience, as it is insufficient to provide adequate converts on its own. Prayer is deemed a fundamental aspect of practice utilised by those throughout the centuries who have had direct religious experiences. In summarizing his series in the final lecture, James expressed the need for toleration of religious diversity and allowance for individuals to pursue their course: ‘some men have the completer experience and the higher vocation, here just as in the social world; but for each man to stay in his own experience, whate’er it be, and for others to tolerate him there, is surely best’. This is necessary because the intellectual underpinning is that there is something wrong with us and that this can be rectified by ‘making the proper connection with the higher powers’. For this reason, a higher value must be given to experience and feeling over thought. In terms of trying to make sense of how this union with God takes place in a scientific context, James argues that the subconscious serves as a conduit through which ‘the further limits of our being plunge, it seems to me, into an altogether other dimension of existence from the sensible and merely “understandable” world’. For James, religious experiences are a reality although they cannot be satisfactorily explained in wholly philosophical or scientific terms: ‘The only thing that it unequivocally testifies to is that we can experience union with something larger than ourselves and in that union find our greatest peace’.