Analysis of Crossed Threads

The silken threads by viewless spinners spun,
Which float so idly on the summer air,
And help to make each summer morning fair,
Shining like silver in the summer sun,
Are caught by wayward breezes, one by one,
Are blown to east and west and fastened there,
Weaving on all the roads their sudden snare.
No sign which road doth safest, freest run,
The wingèd insects know, that soar so gay
To meet their death upon each summer day.
How dare we any human deed arraign;
Attempt to recon any moment's cost;
Or any pathway trust as safe and plain
Because we see not where the threads have crossed?