Book II

Locke establishes that ideas are what the mind is applied to when thinking, and provides examples like whiteness, hardness, and thinking itself to show the diversity of ideas men possess.

Locke acknowledges the received doctrine that men have native ideas stamped upon their minds at birth, which he signals he has examined in the prior book and will now refute.

Locke proposes that the mind begins as blank paper and is furnished entirely through experience—observation of external sensible objects and internal operations of the mind.

Locke identifies sensation and reflection as the only two sources from which all ideas derive, forming the complete material of human knowledge.

Locke defines sensation as the conveying of perceptions of external objects through the senses, yielding ideas of sensible qualities like colors, temperatures, and textures.

Locke defines reflection as the mind's perception of its own operations and activities, yielding distinct ideas of mental processes like thinking, willing, and reasoning.

Locke asserts that every idea the understanding has originates from either external objects affecting the senses or the mind's internal operations, with no exceptions.

Locke invites readers to examine their own thoughts and confirm that all original ideas originate from sensation or reflection, making this verifiable through personal observation.

Locke observes that children gradually acquire ideas through sensation rather than possessing them innately, supporting his experiential account of knowledge acquisition.

Locke explains that individuals differ in their store of simple ideas depending on the variety of objects they encounter and their reflection on mental operations.

Locke explains that children acquire ideas from reflection later than sensory ideas because reflection requires turning attention inward, while sensory stimuli constantly solicit attention outward.

Locke establishes that asking when a man begins to have ideas is the same as asking when he begins to perceive, equating ideas with the act of perception.

Locke identifies the opposing view that the soul constantly thinks and has actual perception from its existence, which he will now refute.

Locke claims that he cannot conceive the soul always thinks and argues that proving this would require demonstrating it against the experience of sleep without dreaming.

Locke argues that thinking should be conceived as an operation or power of the soul, not its essential nature, just as motion is a power of the body, not its essence.

Locke challenges the claim that 'the soul always thinks' is self-evident by appealing to universal human experience and reason rather than mere assertion.

Locke demonstrates that proving the soul always thinks by using that very claim as a hypothesis commits a logical fallacy and proves nothing.

Locke clarifies that he does not deny the soul exists during sleep, only that the soul cannot think without conscious perception, which during sleep is absent.

Locke asserts that consciousness is absolutely necessary to thought—one cannot think without being aware of thinking, unlike other operations the soul might perform.

Locke considers the objection that the soul might think during sleep without the person being conscious of it, and proceeds to refute this idea.

Locke argues that if the soul thinks without consciousness during sleep, then the sleeping man and waking man become two different persons, which is absurd.

Locke presents a hypothetical scenario in which one soul inhabits two bodies to show that unconscious thinking would make personal identity impossible.

Locke argues that people who sleep without dreaming cannot be convinced they had thoughts while sleeping, which refutes the doctrine that the soul always thinks.

Locke identifies the objection that the soul thinks during sleep but memory fails to retain these thoughts, which he then argues is implausible.

Locke argues it is implausible that a person could have extensive thoughts while sleeping and yet retain no memory of them upon waking.

Locke provides empirical evidence that most people sleep without dreaming, supporting the view that the soul does not always think.

Locke argues that if the soul thinks during sleep but retains no memory of these thoughts, such thinking serves no purpose and reflects poorly on divine wisdom.

Locke argues that if the soul possesses innate ideas and always thinks, it should recall these native ideas in dreams, but it does not.

Locke observes that dreams consist of combinations of ideas acquired during waking life, not innate or separate ideas of the soul.

Locke argues it would be strange if the soul possessed innate ideas yet never recalled them in dreams or provided the waking mind with discoveries from them.

Locke challenges those asserting the soul always thinks to explain how anyone can know this about themselves or others without perceiving it.

Locke argues that saying the soul thinks without the person perceiving it is analogous to the nonsensical claim that a body is extended without parts.

Locke demonstrates that thinking, by its nature as conscious activity, cannot occur without consciousness, making unconscious thinking a contradiction in terms.

Locke argues that one cannot know another's thoughts except through their expression, making claims about unconscious thinking unknowable and unprovable.

Locke points out the absurdity that one would claim to perceive another's unconscious thoughts while denying that animals, which show all signs of thinking, actually think.

Locke contends that asserting the soul always thinks by mere definition, without proof, is circular reasoning and cannot establish the doctrine's truth.

Locke concludes from observing children that they possess no innate ideas and acquire all knowledge through sensation and reflection.

Locke observes that newborns show little evidence of thinking and that fetuses in the womb likely exist in a state similar to vegetables without perception.

Locke explains that as children accumulate ideas through sensation, their capacity for thought and reasoning gradually improves through exercise and reflection.

Locke defines the beginning of ideas as coeval with sensation, establishing that ideas and sensation are intimately connected in their origin.

Locke summarizes that impressions from external objects and the mind's reflection on its operations form the original source of all human knowledge and understanding.

Locke establishes that in receiving simple ideas, the understanding is passive and cannot refuse, alter, or create ideas, likening it to a mirror reflecting objects.