> is that an imposition by an external will, or is it closer to gravity and surface tension defining the path of water as it flows down a hill?

It is imposition of the will of capital, as the personification goes. As such it is also the imposition of its representatives - politicians, churches and economists. Even water flowed down hills before capitalism - so the natural analogy is only half way there, perhaps a much more recent (and thoroughly capitalist) natural analogy would do: the pollution of the earth!

More than a bee builds a hive, we're responsible because we are thinking creatures, with the power to change nature and make it ours.

"The institutions of feudalism are artificial institutions, those of the bourgeoisie are natural institutions. In this, they resemble the theologians, who likewise establish two kinds of religion. Every religion which is not theirs is an invention of men, while their own is an emanation from God. When the economists say that present-day relations — the relations of bourgeois production — are natural, they imply that these are the relations in which wealth is created and productive forces developed in conformity with the laws of nature"

On intention, we'd agree that intention is a very human thing. Does the air show intent? Do animals show intent? No, intent is human - and so the force of capital must also be, or so it would go if we don't use the power of abstraction. To think abstractly about the situation, we recognise that abstract entities do have intentions of their own. Socialists don't want to go about blaming, they want to get on finding the most abstract form of this system, which is totalitarian: it absorbs every section of society (from interactions every day, to leisure time, to work time, to our relationships, to art, philosophy, science...) to work for it. If you don't conform as a capitalist or a worker, you're out. Intention is the question when we want to blame someone, but not even Marx blamed (or praised) the capitalists.

"To prevent possible misunderstanding, a word. I paint the capitalist and the landlord in no sense couleur de rose [i.e., seen through rose-tinted glasses]. But here individuals are dealt with only in so far as they are the personifications of economic categories, embodiments of particular class-relations and class-interests. My standpoint, from which the evolution of the economic formation of society is viewed as a process of natural history, can less than any other make the individual responsible for relations whose creature he socially remains, however much he may subjectively raise himself above them."

I think we have reached the point where the growth of the market should be questioned, and whether its worse continuing to serve this external alien authority, both as capitalists and as workers. The question of what follows is to many still an open one, as I'm sure you'd agree if I were to say my own (which you can probably guess is). Can there be a society without the kind of coercion capitalism uses to "redirect our resources"? Maybe you don't think so, but by saying the answer is "no", we're throwing out weighing up its criticism (sociological, economic, moral, artistic) and where it has excelled over any previous system.