[Essay II viii 23-24] As his Royal Society companion Robert Boyle had shown...

[Essay II viii 23-24] As his Royal Society companion Robert Boyle had shown, the rapid motion of insensible particles of matter is a genuine feature of objects, a primary quality that can be transmitted mechanistically from one body to another: as a result, fire has the power to melt other bodies and-in the same way-to produce in us the ideas of warmth, heat, or even pain.

[Essay II viii 15-16] Ideas of Reflection Although he insisted that human awareness begins with simple ideas of sensation, Locke did not believe that they comprise all of our mental contents. We also acquire simple ideas of reflection through an objective observation of our own mental operations.

In any these operations, the human mind must be either passive or active, Locke supposed, and the most fundamental ideas of reflection are therefore just two in number: perception, in which the mind passively receives ideas, and volition, in which it actively initiates something. [Essay II vi 1-2] Every other idea of reflection, on Locke's view, is a simple mode of one or the other of these two basic types. All human mental activities derive from the faculties of understanding and will.

We are naturally familiar with such activities, since they constitute the whole of our conscious thought, but this does not entail our having clear conceptions of them. Familiarity without careful attention provides only confused ideas of our own mental operations. As Locke had already noted, the components of experience we first acquire are vivid sensory impressions of the external world.

It is only with increasing maturity and a capacity for detachment that we grow able to make the careful inward observations from which clear ideas of reflection may arise. [Essay II i 7-9] Even when we have acquired clear ideas from reflection, Locke supposed, we often designate them with a vocabulary drawn from the concrete context of sensory experience, representing our "inner" mental operations by an implicit reference to observable "outer" processes.

[Essay III i 5] The first and simplest of our ideas of reflection is that of perception, the passive reception of ideas through the bodily impressions made by external objects upon the organs of sense. Although perception in this sense is distinguished from thinking generally by the relatively meager degree to which it falls under our voluntary control, Locke believed it always to require some degree of conscious attention.