Naturally, this adds to uncertainty about whether the theory is true, but uncertainty is inherent in any kind of nondeductive inference. Both these methods would guarantee truth, but we know that neither can even begin to account for scientific knowledge. Millgram's argument is not a criticism of a particular theory of coherence, but it is rather an unsatisfiable demand to avoid the inherent uncertainty that accompanies nondeductive inference. Truth is not the only aim of science, which also values explanatory unification and practical application. Species evolve by natural selection.
Lemurs have toes.
Both of these propositions are true, but the first is far more important to science because, as Darwin himself stated, it explains a great number of previously unconnected facts. It is obvious that explanatory coherence furthers the adoption of theories that encourage explanatory unification, because its principle of data priority, E4, encourages the acceptance of observation propositions, and its principle of explanation, E2, encourages the acceptance of hypotheses that explain many observations. Scientists have achieved theories that are at least approximately true. Scientists use explanatory coherence. So explanatory coherence leads to theories that are at least approximately true.