 What, finally, of proximal projections of natural kinds? One plausible line might be to maintain that proximal projections of natural kinds are not themselves natural kinds, hence that they are automatically excluded from the scope of the theory. This plausible line, however, might be the only available line. Presumably, in the course of S’s life, the only way dogs can cause “X”s is by way of causal mediators between the dogs and the “X”s. Thus, each episode in which a dog causes an “X” is also an episode in which a sensory projection of a dog causes an “X”. So, dog efficiency for “X” can be no higher the efficiency of dog sensory projections. And, if it is possible for there to be a sensory projection of a dog without there being an actual dog, then the efficiency of the projections would be greater than the efficiency of the dogs. So, “X” could not mean dog. But, this problem is not necessarily damaging to BTT.