Having failed to learn wisdom from the ant, we now turn to the spider and the bee. Bacon's bee is a charismatic insect and no doubt everybody's paradigm. But it must not be the excuse for begging the question and we do not yet know what the digestive ‘power of its own’ is, nor how it differs from ‘making cobwebs out of their own substance’. Our suggestion is that its power comes from access to necessary truths, which pragmatists cannot abolish nor positivists explain away. These necessary truths are not purely logical. They introduce central concepts which define the subject and scope of theories and state equilibrium conditions which enable models to be solved. This is what we had in mind when proposing that explanation takes place when a conclusion is deduced from a sound and independent theory. So we shall start the present chapter by reflecting further on the nature of necessity and its role in rationalist theories of knowledge. Then we shall put forward our axiomatic model of explanation, claiming that it resolves the persistent puzzle of which generalisations are projectible. Then we shall focus on the application of theory to the world, arguing that economic variables need particular kinds of bearers.