[breck]

I like the "Ladder of causation":

    Rung 1: Associations, observational data (seeing)
    Rung 2: Intervention (doing)
    Rung 3: Counterfactuals (imagining)

I often go in reverse order—let's figure out the cheapest clever ways to prove ship will sink (imagining). Then if it seems like it might float let's build it and throw it on the pond (doing). Then if it seems to float let's hop on board and see what happens.