Well... it might help, sometimes.<p>I think about something like Stokes&#x27; theorem:  The integral of a function over the boundary of a manifold is equal to the integral of the derivative of the function over the interior of the manifold.  But <i>in practice</i>, one integral or the other is often easier to do; that means that the theorem has the practical effect of letting you transform some hard problems into equivalent but easier problems.<p>But note well that I said &quot;<i>some</i> problems&quot;.  There are many problems that this won&#x27;t help with.  There are others where the problem you&#x27;re trying to solve is the easier one, and applying the theorem turns it into a <i>harder</i> problem.<p>I suspect (but do not know) that the Yoneda Lemma is similar.  It can <i>sometimes</i> give you a simpler way of looking at a problem.  But just sometimes.  Sometimes the Haskell&#x2F;ML view is the easiest way to solve the problem you have.  And sometimes it&#x27;s not.