Sometimes, I would maintain, a chalice is just a chalice. Similarly, a hydroelectric plant is just a hydroelectric plant.
Each are made, by humans. Each are examples of technology (Heidegger is I think quite correct to construe "technology" broadly; just about all we do constitutes technology of a sort). Each have a function.
Obviously, they like most everything else can be employed in the fashioning of metaphors. They may be used as examples. Their differences may be noted. They may be subjects of poetry. One might say a chalice, as a sacrificial vessel, and made as one, is in various respects different from a hydroelectric plant, made for quite another purpose. And one might even say that a chalice has a "higher" purpose than a hydroelectric plant (well, someone might). None of this should be surprising. I wonder whether this is, essentially, all that Heidegger is really doing in this essay.
The use of Aristotle's four kinds of causes is interesting. Their use is not explained, however. It appears that Heidegger merely assumes that these are to define our consideration of the question "what is technology?" I'm not so sure. I think it's clear, though, that his use of them serves to guide (or slant as would be said now) the analysis. So, too, with his insistence on defining "technology" and explaining it by reference to the origins of the word in ancient Greek. Why assume that the ancient Greek from which the word may be derived tells us anything regarding how it is used now, or what technology is (what its "essence" is as he insists on putting it)? Why assume that what the ancient Greeks may have thought on this issue is at all pertinent, let alone determinative? Heidegger seems even to acknowledge this, or at least to acknowledge that his technique can form the basis of an objection. But he forges on.
The "monstrous" hydroelectric plant, and apparently modern technology generally, "challenges" nature, it takes from it, according to Heidegger. The plant "commands" the Rhine. Modern technology "expedites" unlocks and exposes the energies of nature. But, he complains, this "expediting" is directed towards another purpose. Coal, he says, has been "hauled out" and stockpiled. Being stockpiled, it is "on call." Heidegger apparently finds this disturbing. Worse than being stockpiled, apparently, is the fact that it is converted to heat (challenging forth the sun's warmth, he says) and then "ordered" to deliver steam to turn wheels that keep a factory running (they must be some wheels).
He contrasts this with the work of the peasant, sowing the fields. This doesn't challenge the soil. The peasant in the sowing of the grain "places the seed in the keeping of the forces of growth and watches over its increase."
I tend to grow a bit suspicious when peasants are referred to this manner, sowing the fields and placing seeds in nature's generous soil, that sort of thing. I suspect the peasant is becoming the subject of a romantic fantasy. Regardless, though, I wonder if Heidegger realized that the happy peasant didn't live on whatever happened to have grown each day. Surely he understood that agricultural produce was regularly stockpiled (like that coal) well before the modern age? It had to be. Winter, most annoyingly, continued to arrive each year, and nothing could be grown then--the "forces of growth" took vacations.
Presumably, Heidegger also realized that sources of heat in addition to coal, such as wood and peat, were stockpiled for future use throughout history, waiting to be "ordered" to produce heat to warm people and their food. One also assumes he was aware of the fact that humans had employed irrigation for thousands of years, "commanding" the waters of rivers to go on unnatural detours.
Heidegger's negative characterizations of modern technology can be applied just as easily to ancient or medieval technology. So, I think he had a tendency to romanticize the past, and that this negatively effected his view of technology. Similarly, he has a tendency to attribute concepts we associate with humans to the objects he idealizes. The chalice is "indebted" to the silver from which it is made, and the silver is "co-responsible" for the chalice. This is most poetic, but that is all it is.
There isn't necessarily something bad about this essay, but there doesn't seem to be anything good about it, either. It's certainly not what I would call an analysis of technology. I don't think it is analytic in any sense. Heidegger clearly feels there's something wrong, or monstrous, with such things as hydroelectric plants that he doesn't feel is wrong with the back-breaking labor of peasants sowing fields by hand (perhaps a plow could be used; it's not clear). But it seems to me that he doesn't explain why he feels this way in any intelligent manner. He characterizes, but provides no justification for his characterizations.