The central Husserlian concept of the directedness of all thought—intentionality—for example, while scarcely mentioned in Being and Time, has been identified by some with Heidegger's central notion of ""Sorge"" (Cura, care or concern). But for Heidegger, theoretical knowledge represents only one kind of intentional behaviour, and he asserts that it is grounded in more fundamental modes of behaviour and forms of practical engagement with the surrounding world. Whereas a theoretical understanding of things grasps them according to ""presence,"" for example, this may conceal that our first experience of a being may be in terms of its being ""ready-to-hand."" Thus, for instance, when someone reaches for a tool such as a hammer, their understanding of what a hammer is is not determined by a theoretical understanding of its presence, but by the fact that it is something we need at the moment we wish to do hammering. Only a later understanding might come to contemplate a hammer as an object. There is thus a sense in which this kind of argument, although very different from Husserlian phenomenology, nevertheless resembles it, to the extent that what is involved is a kind of suspension of the everyday understanding of what it means to experience beings in the world.