In opposition to the rational thinking of the Enlightenment, Romantics often seek the sublime.
"The passion caused by the great and sublime in nature . . . is Astonishment; and astonishment is that state of the soul, in which all its motions are suspended, with some degree of horror. In this case the mind is so entirely filled with its object, that it cannot entertain any other." [Edmund Burke, On the Sublime , 1756 ed. J. T. Bolton. 58]
The Sublime Experience
Sublime experiences, whether in nature or in art, inspire awe and reverence, and an emotional understanding that transcends rational thought and words or language. For Romantics, the sublime is a meeting of the subjective-internal (emotional) and the objective-external (natural world): we allow our emotions to overwhelm our rationality as we experience the wonder of creation.
The Enlightened scientist rationally observes the natural world, isolating and shutting off his emotions and biases to understand objective, quantifiable truths in the form of facts. The Romantic participates emotionally and imaginatively with the natural world, actively breaking down the very same walls so carefully erected by the Enlightenment.
Because the sublime is emotional, it is traditionally considered something one must experience alone. It's no coincidence that Rousseau's last work was titled Reveries of a Solitary Walker. Note how Wordsworth writes of himself experiencing nature alone. Note how Victor Frankenstein finds peace either walking in the mountains or sailing alone. The Romantic does not go up in the hills with his buddies and a 12 pack of Keystone Lite; he wanders the wilderness or back roads alone: the cowboy riding off into the sunset.
Since the sublime is ineffable (beyond words or language), it often best expressed in pure art, such as music. It is no coincidence that Rousseau's contribution to the Encyclopedia focused on music.
Nature and The Irrational Extreme
Following Wordsworth, traditional Romantics associate the sublime directly with nature, and the artist, poet or simply the Romantic experiences the sublime directly witnessing the beauty of nature. But it's important not to confuse or reduce the sublime with simple beauty, rather, Romantics are interested in natural experiences that utterly consume us, perhaps moving us to tears, and giving us a humbling sense of the wonder and majesty of the natural world.
Romantic poets attempt to evoke in their readers a sense of the sublime in part by elevating their language so that it is highly emotional (see Wordsworth; also see Mary Shelley whenever Victor walks alone in the Alps), and in part by embracing the irrational. This second is easily seen in Keats' concept of Negative Capability; we can evoke the sublime in our readers by presenting concepts that can only be grasped intuitively and emotionally, such as joining the irrational opposites of love/death.
Before the Romantics, the sublime is normally related to traditional Christian religion. Note that faith centers around an understanding of truths that transcend rationality, empirical experience, and, often, language: you must feel the Holy Spirit to understand it. Chartres cathedral, or St. Peters Basilica (the Vatican), is designed to represent and evoke the sublimity of God or experiencing the divine; one stands overwhelmed by the immensity and grandeur. Note that all of these sublime experiences simultaneously make us feel small and insignificant as well as in touch with that which has overwhelmed us, be it nature, the universe, or God...or all of these at once.
You Just Gotta Do It, Dude
To understand the sublime, you have to experience it (since ineffable things can't, obviously, be explained!), and the best way to do that from a Romantic standpoint is to go stand at the edge of the Grand Canyon, or drive the Going-to-the Sun highway in Glacier National Park. These views were specifically chosen and designed by American Romantics to evoke the sublime. As the saying goes, Americans have no Chartres cathedral; they have the Grand Canyon.
Quite simply, if you've ever stood alone in the woods, or on the seashore watching the sun set, or on the brink of the Grand Canyon etc., and you found yourself wanting to weep with joy at the beauty of this world, you have experienced the sublime.
And if you haven't, well, you've been missing out.
The 60's drug and hippie culture was directly inspired by the 18th Century Romanticism and is closely connected to the sublime. LSD was supposed to "expand one's cosmic consciousness" via routes previously explored by Coleridge and other Romantic poets. Even the long hair and flowing sleeves and scarves of hippie style was inspired by old paintings of men like Byron, as was sexual libertine-ism and a willingness to push one past extremes.
These were in turn originally inspired by Romantic Neo-Classicism: a renewed interest in Greco-Roman Dionysian and Bachanal-ian drug excess.
Post Hippie Sublime
Post-Romantics, by the way, may seek the sublime in urban or social settings, often including ones that, as Edmund Burke first proposed 250 years ago, are violent. Standing in downtown Manhattan and looking up, or atop the Twin Towers and looking down, or standing in front of a wall of speakers blasting Green Day (sellouts!) or DragonForce (a band which, by the way, sucks!) and slam dancing, or overdosing on caffeine and driving alone through the LA freeways at 2 a.m. at 95 mph...all these are attempts to capture that moment when the outside experience and your imagination overwhelm you and you feel connected to the larger experience of existence. It's no coincidence, then, that the leader of Sublime died of a heroin overdose.
The consumer-market driven Romantic sublime lives on in "extreme sports" like rock climbing, mountain biking and downhill skiing, not to mention sky diving and bungee jumping, alligator wrestling, random dumb-ass shit usually accompanied by the words "Hey y'all, watch this! Oh sheeeeeeeit...." and ending in medical evacuation.