I first read this whilst completing a masters dissertation on Heidegger. I got to page 21 and had to stop in complete disagreement with Harman. I thought, 'how can he misunderstand Being and TIme so fundamentally? - I remember asking Ray Brassier about this book 'tool being' -was it any good or completely wrong-headed? Anyway, i didn't read it again, as i thought it was thoroughly misguided in its claim that objects in themselves could be both present and ready to hand independently from Dasein (and other claims that all objects were also 'dasein').
However, i have recently returned to it again. Harman makes a lot of sense, and he makes a lot of sense in a clear and lucid style - although there is a bit of repetition.
The title `tool-being' is Harman's reconceptualising of Heidegger's `ready to hand' as the ontologically primary point of meaning of objects (ie their invisibility in use). However, Harman takes this notion and applies it directly to objects independently of dasein.
Harman's book explores the single Heideggerian theme of present at hand and ready to hand. Traditionally, everything read as `present' is misread, bypassing temporality; whilst the `ready to hand' (typically the door know we use to open a door, or pen we use for writing, or oxygen we use to breath, etc) is invisible through its very habituated use. The ready to hand is the true ontological realm - as being invisible - as it is the mode in which `we' (dasein) most commonly interact with the world, untheoretically - if we start to inspect the door know/the pen/air we breath, then typically we break out of ready to hand mode, enter present at hand mode and are unable to open the door/write something/become conscious of how we breath, thereby entering the Cartesian mode of subject over against object/ becoming thematically aware of objects. Simply, the invisible realm of readiness to hand reveals the true `being' of objects, because it is what absorbs us most completely everyday and because anything deemed merely `present at hand' falls back upon the metaphysics of presence (ie that the essence of the thing present conceals a more fundamental realm beneath it).
Harman reads Heidegger against the typical subjectivist readings by showing that both Zuhanderheit (ready to hand) and Vorhanderheit (present at hand = excuse the spellings) belong equally well to all entities and not merely objects 'encountered' by dasein - 'no humans need exist in order for the paper screen to resists dust or perish by fire' (p.34) - yet these objects still encounter each other in a meaningful way. what is so exciting about the speculative realist movement is this very idea that 'meaning' is not the sole reserve of us human beings - whilst Harman elaborates this lack of meaning in a playful way, Brassier pushes this towards a fascinating, though not a 'superficial' nihilism.
Harman, along with other speculative realists, also seeks to undermine the 'relationality theory of reality' (p.23) by showing how objects have their own independent reality
The meaning of objects does not reside in their relations with dasein, as if objects are mere dead matter until brought to life through dasein's use. Neither is the meaning, the being, of objects in their relations , or `being-towards...' - no. the meaning of objects resides in the objects themselves. Handling and theorizing (Zuh...and Vorh..) are human centered (p.152). objects relate not just to human beings, but to each other (169). Whilst hammering a nail, the end of the hammer and the nail encounter one another as objects. Obviously there is no question here of either objects being consciously aware of each other. However, they do encounter each other in terms of present at hand and ready to hand entities. How? During this encounter, the fork of the hammer disappears into an unknown alien universe of its own, since it has become ready to hand to the nail (ie, is not encountering it, but is still part of the hammer). The point is, the fork does not disappear into its own usefulness (in the traditional Heideggerian reading) since it is not actually being used, it just disappears from its object. There is no dasein involved here - ie the hammer could have just fallen onto the hammer. In other words, every object is both singular and relational - so there IS such a thing an individual equipment. MOrever, every object is more than its mere relationality and its present at hand or readiness to hand: the object's being is beyond the reach of both dasein and other objects which it might encounter.
Objects exist independently of dasein - and objects reduce each other to present at hand entities - it is not just dasein that does this. A billiard ball encounters another billiard ball, reducing the other ball to its pure mass (ball A is not interested in the colour of ball B for instance).
Tool being is an easier read than Nihil Unbound, but not as vital as Meillasoux's ground-breaking Beyond Finitude. Harman's other book `The Quadruple object' reads as a simplified/summarized version of Tool Being - although I'm saying that having only got to page. 80 so far.
There is only one negative I can find in tool being and that is that Harman does not leave himself enough room to fully outline his theory of objects in greater detail. I think he probably does go on to outline his object orientated philosophy in guerilla metaphysics.
Excellent original reading of Heidegger.