Abandoning unicity is certainly a radical proposal, comparable in the history of science to the radical step our intellectual ancestors took when they replaced the centuries old notion of an immovable earth with the modern concept of a spinning planet in motion around the sun. In making that transition it was important to develop an understanding of why the earlier ideas worked so well; e.g., why one did not feel the earth was moving. By analogy it is helpful to note, as discussed in section 6, that from a quantum perspective the macroscopic world of everyday experience can be understood for all, or almost all, practical purposes using a single quasiclassical framework. Within that framework the principle of unicity holds, and one can thus understand why it was quite satisfactory before the quantum revolution, and remains so in sciences where specific quantum effects do not need to be taken into account. See the   Further Reading supplement for a more extended discussion.