Out from the Heart is a short companion work in which James Allen develops a single idea: as the heart, so is the life. He pictures the inner life as a hidden spring from which all that a person is and does issues, so that thoughts engendered in the heart at last reveal themselves in words, actions, and accomplished things. Outer conditions are the shadow and effect of inner states.
From this foundation Allen turns to the nature of mind. He calls the mind the arbiter and shaper of conditions, weaving character on the loom of life from the thread of thought. Crucially, he holds that the bonds of habit and weakness are self-made and exist nowhere but in one's own mind; because a person compounded that mind by past thoughts and deeds, the same person retains the power to refashion it by choice.
The central practical chapter concerns the formation of habit. Every established mental condition is described as an acquired habit, built up by the continuous repetition of a thought until it becomes fixed and automatic. Allen presses the encouraging corollary: just as harmful habits are formed by repetition, good habits are formed the same way, and through practice right thought can become as natural and easy as a learned craft.
Allen then argues that doing precedes knowing. Spiritual principles cannot be grasped by reading theology or metaphysics; they are reached only after long discipline in the practice of virtue. He illustrates with the schoolmaster, the apprentice, and the well-governed child, all of whom must practice the simple lesson before the underlying principle can be understood. Virtue can only be known by doing.
The later chapters make this concrete. Allen groups the first steps of the higher life into graded lessons, beginning with the discipline of the body, then of speech, then of inclination, and he tabulates wrong and right mental conditions alongside their effects on life. The closing exhortation states the book's temper plainly: there is no lazy way to truth, discipline itself is beautiful, and the seeker who fails and rises again will reach the summit so long as the path is not abandoned.