George Grote opens his review by noting that Mill's octavo volume of twenty-eight chapters and 560 pages contains 'no superfluous sentences, scarcely even a superfluous word.' This economy of expression, Grote argues, demands 'a full stretch of attention' from readers. The review itself mirrors that density, packing sharp criticism into a compact space. Grote positions Mill and Hamilton as 'two most conspicuous representatives of the modern speculative mind of England,' setting up a direct antithesis that structures the entire critique.

The Antithesis of Two Thinkers

Grote wastes no time establishing the stakes: Hamilton's influence on a generation of students through his Edinburgh lectures is contrasted with Mill's challenge to that legacy. Grote notes that Hamilton 'kept up the idea of philosophy as a subject to be studied from its own points of view,' a dignity he thinks had receded in England. Yet Grote does not count himself among Hamilton's followers. He praises Hamilton's service in piecing together philosophical traditions but implies that Mill's work forces a reckoning with those traditions. The review thus frames the book as a confrontation between two systems, not merely a critique of one.

The Psychological Theory and the Need for Observation

Grote zeroes in on Mill's psychological theory, which holds that what seems a 'mental integer' was once 'a multiplicity of separate mental fragments.' He argues that the theory finds little acceptance because few observers have trained themselves in 'inductive logic' to study the 'latens processus' of mental development. Grote cites the case of Platner, who used the Method of Difference to study a congenital defect of sense, as a rare example of careful observation. He laments that mental philosophers, unlike chemists and physicists, have been 'careless about enlarging, varying, authenticating their records of particular facts.' This methodological critique is central to Grote's assessment.

Hamilton's Blindness to Mental Facts

Grote finds it 'extraordinary' that Hamilton and Mansel could declare that certain beliefs must be 'a priori' and cannot be engendered by experience. He notes that Hamilton, despite his vast acquaintance with human belief's diversities, never brought that knowledge to bear when assuring students that custom and association were insufficient to produce a 'felt necessity of believing.' Grote accuses Hamilton of being 'blind to obvious facts contradicting the principles which they lay down.' This section highlights Grote's insistence that philosophical claims must be tested against observable mental phenomena, a standard he finds Hamilton fails to meet.

Unconscious Modifications and the Limits of Evidence

In discussing Mill's examination of Hamilton on unconscious mental modifications, Grote notes that Mill is 'inclined to admit unconscious mental modifications' but only in the sense of 'unconscious modifications of the nerves.' Grote points out that Hamilton's reasoning on mental latency is 'confused' and his refutation of Dugald Stewart inconclusive. The review here shows Grote's careful parsing of arguments: he distinguishes between what Mill accepts (the possibility of unconscious neural processes) and what he rejects (Hamilton's vague conception of latency). This precision reflects Grote's own philosophical method, which values clarity and evidence over speculative metaphysics.

Grote's review is best read as a companion to Mill's original work, not a substitute. It assumes familiarity with both Mill's arguments and Hamilton's positions. Readers new to the debate may benefit from first consulting Mill's chapter on the psychological theory and Hamilton's lectures on logic and metaphysics. Grote's sharp focus on method and evidence provides a model for evaluating philosophical claims, but his own biases—particularly his commitment to empirical observation—should be weighed against the intuitionist tradition he critiques.