For Heidegger, thinking about technology starts with the ancient Greeks. In Plato, techne is part of the arts (poeisis). In Latin, technology is understood as instrumentum. Now technology means 1) human activity; 2) means to an end. Heidegger argues against this “correct” view of technology as instrumentum. For him, technology is a mode of revealing, or aletheia (usually translated as “truth” but H. tries to change this) as in Plato. Technology is how things come to presence, that is, in German, Entbergen. H. uses German words to understand the essence–Wesen, not as essentia–of technology.
How is technology destroying man’s relationship to Being? Because of what Heidegger names as the standing-reserve (Bestand-Gestell). The airplane or the hydroelectric plant in the Rhine River store energy, and do not let us experience Being in its essence. By contrast, the silver chalice of the religious ceremony or the simple windmill lets us experience Being as Entbergen.
What does H. propose? Listen and obey the call of Being. Like the poet Holderlin, H. thinks that within the danger of the standing-reserve of technology, a saving power will present itself, if we let it.