To me, this chapter seems to basicly be explaining the reasons that utopian socialism developed. I think Engels is pointing out that the utopian thinkers were thinking too abstractly, and they had no actual concrete analysis, and allowed their subjective thoughts to get in the way.
"The great thinkers of the 18th century could, no more than their predecessors, go beyond the limits imposed upon them by their epoch."
I think that quote sums up the chapter fairly nicely.
"Revolutions are the locomotives of history."
<Armchair> so, i just figured out, the phone doesn't fit any of the holes in the back of the computer