The writings of the English Romantics were a reaction to the Age of Enlightenment or the Age of Reason.
The enlightenment was a movement of science and reason.
It was a time similar to the "hippie movement" in the U.S. during the 1960s. People questioned...
....traditional institutions, customs, and morals...
Much more emphasis was place on "rationality." For the Romantic authors, there was no place for the rational. The interest in science had misdirected people (the Romantics felt) away from the natural world, one of the many things they praised in their writing. The Englightenment movement took place during the 18th Century.
Often referred to as the first-generation Romantic poets, Wordsworth and Coleridge together published their collection of poetry entitled, Lyrical Ballads in 1798 (which often signals the start of the movement). They would be followed by Byron, Shelley and Keats. Though the movement would last only a short time (until 1832 or thereabouts), it was a golden period in which masterful writing was generated by these and other Romantic writers.
One piece of writing that reflected the dangers of the Age of Enlightenment was Mary Shelley's Frankenstein, where Victor Frankenstein lets science and a thirst for knowledge destroy him and those he loves when he creates life—acting like God. The moment when Victor masters the essence of life is captured in Chapter Four of the novel:
After days and nights of incredible labour and fatigue, I succeeded in discovering the cause of generation and life; nay, more, I became myself capable of bestowing animation upon lifeless matter.
We should note Shelley and her work...
...its emphasis on: feelings over intellect and the dangers of relying exclusively on intellect...
Among a great many descriptions of the majesty of nature, Shelley also includes...
...the sadness inherent in the human ability to corrupt what should be naturally good.
A poem that rejects the era of enlightenment is by Samuel Taylor Coleridge, called "Frost at Midnight." In it, his hope is that his son (unlike himself) will grow up surrounded by the wonders of nature...
For I was reared
In the great city, pent 'mid cloisters dim,
And saw nought lovely but the sky and stars.
Coleridge writes of his youth's lack of the beauties of nature; he remembers seeing nothing but stars and sky between buildings. However, for his son, his wishes are much greater...
But thou, my babe! shalt wander like a breeze
By lakes and sandy shores, beneath the crags
Of ancient mountain, and beneath the clouds,
Which image in their bulk both lakes and shores
And mountain crags: so shalt thou see and hear
The lovely shapes and sounds intelligible
Of that eternal language, which thy God
This poem speaks of what existed for Coleridge, growing up, when nature was not extolled; but he sees in the Romantic movement hope for his son that he will know the magnificence of nature, and be moved by it as opposed to the lifeless, rational study of science and man's attempt to master the natural world.