This trope is not to be confused with the philosophies of Idealism and Cynicism.
Originally, Idealism was the philosophy of perception that the world is composed of, or heavily dependent on mind, ideas or perception. Epistemological Idealists, like Kant, claim that the only things which can be directly known for certain are just ideas (abstractions. In other words, idealism simply meant that You Cannot Grasp the True Form of actual reality, and that what you see are just projections in your mind/brain). Such idealism is commonly associated with the philosophies of Plato and his idea of a "World Of Forms". In the Theory of Forms, our world is just a shadow of more complicated and perfect ideas. Similar ideas can be found in Hinduism, which the view that consciousness, which at its root emanates from God (Brahman, Purusha or Svayam bhagavan), is the essence or meaning of the phenomenal reality. One of the best analogies for this kind of idealism is The Matrix. Nowadays, such beliefs where the world is a projection of subjective experience is more commonly known as "solipsism", and here on Tv Tropes, we prefer to use idealism in its simpler and more literal definition, that is, "belief in ideals".
Cynicism (from the word kynikos, "dog-like" and that from κύων, kyôn, "dog") was the philosophy that proposes virtue as the greatest good, and rejection of conventional notions of happiness like those gained from idealism and materialism (which means, Original Cynicism has more in common with Stoicism and Buddhism than with Pessimism and Nihilism). The Cynics of these times even believed that people could gain happiness through a rigorous training and living a simple life that is in agreement with Nature (Which was pretty idealistic if you think about it). But the majority of the Cynics took it to its logical extreme. They lived a life of poverty, were highly indifferent, harshly criticized the wealthy and idealistic, and generally lived in a way that could best described as "dogs" (There are four reasons why the Cynics are so named. First because of the indifference of their way of life, for they make a cult of indifference and, like dogs, eat and make love in public, go barefoot, and sleep in tubs and at crossroads. The second reason is that the dog is a shameless animal, and they make a cult of shamelessness, not as being beneath modesty, but as superior to it. The third reason is that the dog is a good guard, and they guard the tenets of their philosophy. The fourth reason is that the dog is a discriminating animal which can distinguish between its friends and enemies. So do they recognize as friends those who are suited to philosophy, and receive them kindly, while those unfitted they drive away, like dogs, by barking at them.). In contemporary times, the negativity and harsh scepticism of cynicism made thinkers in the late 18th and early 19th century consider it as a pessimistic philosophy.