Critical evaluation and contemporary relevance of the text practice questions.

A standard objection to the city-soul analogy in Plato's Republic is that

• a city may count as just only because the people in it are just, so the transfer fails
• Plato never says which class in the city answers to which part of the soul
• the city described is imaginary, and no argument may appeal to an imagined case
• justice in a city is a matter of law, so the work should have examined actual legal codes

Answer: a city may count as just only because the people in it are just, so the transfer fails

The objection attacks the inference between the two levels: if the city is called just in virtue of its citizens, the analogy presupposes the account of the individual it was meant to deliver. It is distinct from the political complaint about rule by philosophers, which targets the proposal rather than the analogy.

In The Open Society and Its Enemies, Karl Popper's criticism of Plato's Republic is that

• Plato's political proposals are sketched too thinly to be assessed as a programme at all
• claims about the Forms cannot be falsified, so Plato's metaphysics is strictly meaningless
• the ideal city is a closed society whose rulers claim authority from knowledge
• Plato takes democracy seriously enough to give it the strongest defence then available

Answer: the ideal city is a closed society whose rulers claim authority from knowledge

Popper's charge is political: the Republic is read as a programme for arresting social change and vesting authority in those who claim to know. His falsifiability criterion belongs to his philosophy of science and is not the objection he brings here, and a test of meaningfulness is the logical positivists', not Popper's, whose criterion demarcates science rather than meaning.

In her correspondence with Descartes about the Meditations, Princess Elisabeth of Bohemia presses him to explain how

• a perfectly good God could permit a person to be deceived about arithmetic
• an unextended thinking thing can move an extended body
• clear and distinct perceptions can be had by a mind that is joined to a body
• the wax example can be squared with what the senses report about bodies in Meditation VI

Answer: an unextended thinking thing can move an extended body

This is the interaction problem: dualism assigns mind and body natures that seem to rule out causal contact, and Elisabeth asks for the mechanism. It targets the two-substance commitment, not the cogito, and occasionalism and parallelism are later attempts to answer it by denying direct interaction.

Legal moralism, as pressed against the argument of Mill's On Liberty in the Hart-Devlin debate, holds that

• the law may restrict conduct only where a definite harm to another can be shown
• the proper aim of the criminal law is to maximise welfare, whatever conventional morality says
• conduct that damages only the agent may be restricted for that agent's own good
• society may enforce its shared morality, because that morality holds it together

Answer: society may enforce its shared morality, because that morality holds it together

Devlin holds that a shared morality is part of what holds a society together, so society may use the law to protect it; Hart replies that no evidence connects tolerated immorality with disintegration. Legal moralism must not be confused with paternalism, which restricts conduct for the agent's own good rather than to protect the community's code.

Sachs raised a well-known objection to the Republic. His charge is that Plato

• fails to describe the institutions of the just city in sufficient detail to be assessed
• defends a psychological harmony under the name of justice, without showing that a person in that state will do the things ordinarily called just
• relies on a theory of the Forms which is not introduced until the later books of the work, so that the argument of the earlier books cannot rely upon it
• assumes that the city and the soul must have the same number of parts

Answer: defends a psychological harmony under the name of justice, without showing that a person in that state will do the things ordinarily called just

The objection is that the argument changes the subject: Glaucon asked why one should refrain from theft and betrayal, and the answer describes an inner ordering. Defenders reply that Plato supplies the missing link by arguing that a soul so ordered would have no motive for such acts.

Mill's argument in On Liberty is often applied to the regulation of speech on large online platforms. The feature of the contemporary case that puts most pressure on his argument is that

• the arguments for free discussion were formulated before the invention of the printing press, which changed the scale of publication entirely
• speech now reaches audiences at a scale and speed at which correction may not catch up with the original claim
• online speech is written rather than spoken, and Mill discusses only spoken discussion
• platforms are privately owned, and Mill's principle concerns only the actions of governments

Answer: speech now reaches audiences at a scale and speed at which correction may not catch up with the original claim

Mill's case rests on a mechanism: error is exposed by contest and truth gains from the collision. Where a false claim reaches millions and its correction reaches a fraction of them, the mechanism is impaired, which is a more serious challenge than any point about the medium.