One way to do that is to see causality as going from the construct to the items—the measurer assumes that the respondent "has" some amount of the construct, and that amount of the construct is a cause of the responses to the items in the instrument that the measurer observes. That is the situation shown in Fig. 1.4—the causal arrow points from left to right. However, this causal agent is latent—the measurer cannot observe the construct directly. Instead the measurer observes the responses to the items and must then infer the underlying construct from those observations. That is, in Fig. 1.4, the direction of the inference made by the measurer is from right to left. The remaining two building blocks embody two different steps in that inference. Note that the idea of causality here is an assumption; the analysis does not prove that causality is in the direction shown, it merely assumes it goes that way. In fact the actual mechanism, like the construct, is unobserved or latent. It may be a more complex relationship than the simple one shown in Fig. 1.4. Until research reveals the nature of that complex relationship, the measurer is forced to act as if the relationship is the simple one depicted.