The Edinburgh Lectures gather a course Troward delivered in Edinburgh into a short, systematic statement of what he calls Mental Science, the New Thought theory of how mind relates to matter. He proceeds from first principles toward practice, building each lecture on the last so that the later claims about healing and growth rest on the earlier claims about spirit and intelligence.
He starts by questioning the ordinary contrast between living spirit and dead matter. Since physical science shows that even a lump of steel is full of atomic motion, motion cannot be the dividing line. The true measure of livingness, Troward argues, is intelligence, which rises by degrees from plant to animal to the human mind. At the top sits a cosmic intelligence inherent in the life-principle itself, and the human capacity for individual volition is the latest product of that same evolutionary movement.
The central technical move is the division of mind into two modes. Citing the hypnotism of his period, Troward describes an outer objective mind that can reason inductively, comparing facts to reach general principles, and an inner subjective mind that reasons only deductively, accepting whatever suggestion it is given and working it out with strict logic. The subjective mind is the builder of the body and the seat of intuition, but it is under the control of the objective mind and of suggestion. He also holds that the universal mind is purely subjective, so it too accepts the ideas impressed on it.
From this he develops his account of causation. Conditions, whether positive or negative, are never primary causes; they are links in a chain of secondary causes stretching out of the past. The only escape from this iron sequence is to rise to the region of pure ideas within, where a thought-image acts as a relative first cause for its object. Treating the ideal as the real, rather than waiting on circumstances, is for Troward the difference between consciously using first cause and drifting under secondary causation.
The practical heart of the book is the law of growth. Thought forms a spiritual prototype that, left undisturbed, reproduces itself in outward circumstances, so the task is to sow the seed and trust its inherent vitality rather than to force results. Anxiety and despair plant an opposite prototype and undo the work. The closing lectures extend this to body, soul, and spirit, ending with the claim that the originating spirit is creative, affirmative, and best named as Love expressing itself in Beauty. The page characterizes this argument without endorsing its metaphysical or therapeutic claims.