What is a monster? A being whose survival is incompatible with the existing order.
Interpretation
A monster is defined as something that cannot coexist within the current societal structures.
Denis Diderot's quote reflects on the nature of monsters as beings that challenge or disrupt the established norms and order of society. This could apply to individuals or ideas that are seen as threats because they do not conform to the accepted ways of living or believing, ultimately leading to conflict between the entity and its environment.
In practice
In a debate about societal norms, one might reference this quote to illustrate how individuals or ideas that challenge the status quo are often labeled as 'monsters'.
The arbitrary rule of a just and enlightened prince is always bad. His virtues are the most dangerous and the surest form of seduction: they lull a people imperceptibly into the habit of loving, respecting, and serving his successor, whoever that successor may be, no matter how wicked or stupid.
This root [the potato], no matter how much you prepare it, is tasteless and floury. It cannot pass for an agreeable food, but it supplies a food sufficiently abundant and sufficiently healthy for men who ask only to sustain themselves. The potato is criticized with reason for being windy, but what matters windiness for the vigorous organisms of peasants and laborers?
Do you see this egg? With this you can topple every theological theory, every church or temple in the world.
There are three principal means of acquiring knowledge... observation of nature, reflection, and experimentation. Observation collects facts; reflection combines them; experimentation verifies the result of that combination.
In order to get as much fame as one's father one has to much more able than he.
All abstract sciences are nothing but the study of relations between signs.
I love the pure, peaceable, and impartial Christianity of Christ; I therefore hatethe corrupt, slaveholding, women-whipping, cradle-plundering, partial, and hypocritical Christianity of this land. Indeed, I can see no reason, but the most deceitful one, for calling the religion of this land Christianity. I look upon it as the climax of all misnomers, the boldest of all frauds, and the grossest of all libels.
When childhood dies, its corpses are called adults and they enter society, one of the politer names of hell. That is why we dread children, even if we love them, they show us the state of our decay.
Life is divided into the horrible and the miserable.
Everybody is special. Everybody. Everybody is a hero, a lover, a fool, a villain. Everybody. Everybody has their story to tell.
Religion was fading into the background. He had shovelled away all the beliefs that would hamper him, had cleared the ground, and come more or less to the bedrock of belief that one should feel inside oneself for right or wrong, and should have the patience to gradually realise one's God. Now life interested him more.
If you hear a "prominent" economist using the word 'equilibrium,' or 'normal distribution,' do not argue with him; just ignore him, or try to put a rat down his shirt.
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