处：位于, to be situated, (postion in relation to something else)
在…中 — In the process of
中 here is used after a verb or verbal phrase to indicate in the process of, or within something. It is often used to emphasize the immediacy of one’s location or situation.
例 — Examples
• 建筑还在建设中。 This building is still under construction.
• 我在地铁中。 I'm in the subway.
There are several symmetries of thought within this poem.
This poem was written in an era when the ascent to prestige was especially treacherous and difficult. Many were put off by the arduous Civil Service exams, which required years of study, as well as the political infighting that awaited them if they passed. Confucianism (儒家), Taoism (道家), and Buddhism (佛家) were the dominant philosophies of the day, and they shared similar outlooks on what it meant to have a good life:
Confucianism: Accept whatever comes your way and be content with your lot.
Dàojiā: Zhīzú bù rǔ
Daoism: If one knows contentment, one will not desecrate one’s body.
Buddhism: The physical world is illusory.
Put off by high society and emboldened by philosophy, some decided to throw caution to the wind and retreat far into the countryside. Thus many of China’s greatest poets wiled away their days drinking and reading books. In the seclusion of the mountains, they were free to experiment in their pursuit of their good life. Jia Dao alludes to the three major schools of thought as objects within the poem. Confucianism takes the form of松下, or under the pine tree, Daoism of 采药, or medicinal herbs, and Buddhism of 云深 or deep fog.
The lifelong spiritual journey of the individual is found in the poem’s thematic structure. In this first line, Jia Dao asks the hermit’s apprentice where to find his master, embarking on his quest. In the second and forth lines, his hopes are dashed — the hermit is collecting herbs and it’s too foggy to see him. In other words, the first and third lines of this poem are optimistic, and the second and fourth are pessimistic. In these lines, Jia Dao seems to suggest an inherent balance — to be an individual is a process of perpetual becoming, with all of its starts and stops.
Shortcut to fame or success
In the Tang Dynasty, official Lu Zangyong was famous for living in seclusion at Zhongnan Mountain, just south of Xi’an in Shanxi. His friend, Sima Chengzhen, wryly suggested that living in Zhongnan Mountain was a shortcut to the high government position Lu eventually secured in Chang’an.
Original Source: The New Book of Tang, Lu Yangyong Biography