In higher organisms (like people), these two modes of perception combine into what Whitehead terms "symbolic reference", which links appearance with causation in a process that is so automatic that both people and animals have difficulty refraining from it. By way of illustration, Whitehead uses the example of a person's encounter with a chair. An ordinary person looks up, sees a colored shape, and immediately infers that it is a chair. However, an artist, Whitehead supposes, "might not have jumped to the notion of a chair", but instead "might have stopped at the mere contemplation of a beautiful color and a beautiful shape." This is not the normal human reaction; most people place objects in categories by habit and instinct, without even thinking about it. Moreover, animals do the same thing. Using the same example, Whitehead points out that a dog "would have acted immediately on the hypothesis of a chair and would have jumped onto it by way of using it as such." In this way symbolic reference is a fusion of pure sense perceptions on the one hand and causal relations on the other, and that it is in fact the causal relationships that dominate the more basic mentality (as the dog illustrates), while it is the sense perceptions which indicate a higher grade mentality (as the artist illustrates).
How does Whitehead describe the process of a typical person noticing a chair?
An ordinary person looks up, sees a colored shape, and immediately infers that it is a chair

Leakage is equivalent to a resistor in parallel with the capacitor. Constant exposure to heat can cause dielectric breakdown and excessive leakage, a problem often seen in older vacuum tube circuits, particularly where oiled paper and foil capacitors were used. In many vacuum tube circuits, interstage coupling capacitors are used to conduct a varying signal from the plate of one tube to the grid circuit of the next stage. A leaky capacitor can cause the grid circuit voltage to be raised from its normal bias setting, causing excessive current or signal distortion in the downstream tube. In power amplifiers this can cause the plates to glow red, or current limiting resistors to overheat, even fail. Similar considerations apply to component fabricated solid-state (transistor) amplifiers, but owing to lower heat production and the use of modern polyester dielectric barriers this once-common problem has become relatively rare.
With what value is a resistor in parallel with a capacitor equal to?
Leakage

The Republic of Letters was the sum of a number of Enlightenment ideals: an egalitarian realm governed by knowledge that could act across political boundaries and rival state power. It was a forum that supported "free public examination of questions regarding religion or legislation". Immanuel Kant considered written communication essential to his conception of the public sphere; once everyone was a part of the "reading public", then society could be said to be enlightened. The people who participated in the Republic of Letters, such as Diderot and Voltaire, are frequently known today as important Enlightenment figures. Indeed, the men who wrote Diderot's Encyclopedie arguably formed a microcosm of the larger "republic".
Who were two of the figures that participated in the Republic of Letters?
Diderot and Voltaire