A motion and a spirit, that impels All thinking things, all objects of all thought, And rolls through all things.
The speaker defines the "something" with a little more detail. It's "a motion and a spirit," that "impels," or animates, all things that think, and that "rolls through all things" (102).
He repeats the word "all" four times in two lines. He really wants to emphasize that this "spirit" connects everything.
The more we read, the more we're convinced that George Lucas read "Tintern Abbey" before writing Star Wars.
Therefore am I still A lover of the meadows and the woods, And mountains; and of all that we behold From this green earth; of all the mighty world Of eye, and ear, – both what they half create, And what perceive;
This is why the speaker still considers himself a "lover" of nature. It's because he's figured out that the "presence" (a.k.a. the "something" or the "motion" or the "spirit") connects everything.
So the speaker loves everything "that we behold/ From this green earth" (104-5), everything that you can sense with "eye, and ear" (106).
"They," in line 106 refers back to the "eye and ear" from earlier in the line.
So the speaker is saying that he loves what his "eyes and ears" "half create" (106) as well as "what [they] perceive" (107).
This is odd. We usually think of our sensory perception of the world – our vision and hearing – as giving us hard facts about the world around us. But here, the speaker suggests that our "eyes and ears" somehow "half create" the things that we see and hear.
well pleased to recognise In nature and the language of the sense, The anchor of my purest thoughts, the nurse, The guide, the guardian of my heart, and soul Of all my moral being.
The speaker is happy to see the "presence" (a.k.a. the "something" or the "spirit") "in nature and the language of the sense" (in other words, in his own sense perceptions).
Only this time, the speaker comes up with yet more ways of referring to the "presence": he calls it "the anchor of my purest thoughts, the nurse,/ The guide, the guardian of my heart, and soul/ Of all my moral being" (109-111).
The speaker seems to find it difficult to describe the "presence" he feels in nature. Up to this point, he's described it as: "a presence" (94), "something" (96), "a motion and a spirit" (100), "the anchor of my purest thoughts" (109), "the nurse, the guide, the guardian of my heart" (109-110), and the "soul of all my moral being" (111).
Clearly, this "presence" is very important to the speaker's spirituality if it's the "anchor" that keeps his "thoughts" pure, as well as the "guardian of [his] heart" and the "soul" of his "moral being."