phenomenon of the "as" a theme and delimit the conception of this 'schema' existentially.
The question of the genesis of theoretical behaviour is one which we have left hanging. What can a temporal characterization of circumspective deliberation and its schemata contribute to the answering of it ? Only that this elucidates the Situation in which circumspective concern changes over into theoretical discovering-a Situation of the kind which belongs to Dasein. We may then try to analyse this change-over itself by taking as our clue an elementary assertion which is circumspectively deliberative in character and the modifications which are possible for it.
When we are using a tool circumspectively, we can say, for instance, that the hammer is too heavy or too light. Even the proposition that the hammer is heavy can give expression to a concernful deliberation, and signify that the hammer is not an easy one-in other words, that it takes force to handle it, or that it will be hard to manipulate.1 But this proposition can also mean that the entity before us, which we already know  circumspectively as a hammer, has a weight-that is to say, it has the 'property' of heaviness : it exerts a pressure on what lies beneath it, and it falls if this is removed. When this kind of talk is so understood, it is no longer spoken within the horizon of awaiting and retaining an equipmental totality and its involvement-relationships. What is said has been drawn from looking at what is suitable for an entity with 'mass'. We have now sighted something that is suitable for the hammer, not as a tool, but as a corporeal Thing subject to the law of gravity. To talk circumspectively of 'too heavy' or 'too light' no longer has any 'meaning' ; that is to say, the entity in itself, as we now encounter it, gives us nothing with relation to which it could be 'found' too heavy or too light.
Why is it that what we are talking about-the heavy hammer-shows itself differently when our way of talking is thus modified ? Not because we are keeping our distance from manipulation, nor because we are just looking away [absehen] from the equipmental character of this entity, but rather because we are looking at [ansehen] the ready-to-hand thing which we encounter, and looking at it 'in a new way' as something present-at-hand. The understanding of Being by which our concernful dealings with entities within-the-world have been guided has changed over. But if, instead of deliberating circumspectively about something ready-to-hand, we 'take' it as something present-at-hand, has a scientific attitude thus constituted
1 'Auch der Satz: der Hammer ist schwer, kann einer besorgenden Überlegung Ausdruck geben und bedeuten: er ist nicht leicht, das heisst, er fordert zur Handhabung Kraft, bzw. er wird die Hantierung erschweren.' Here Heidegger is exploiting the double meaning of the German pair of adjectives, 'schwer' and 'leicht', which may correspond either to the English pair 'heavy' and 'light', or to the pair 'difficult' and 'easy'.