Thisbook isnotatextbook tobecomeacquainted with thelaws ofnature. An elementaryknowledgeaboutlawsofnature, inparticularthelawsofphysics, is presupposed. Thebookisratherintendedtoprovideaclari?cationofconcepts and properties of the laws of nature. The authors would like to emphasise that this book has been developed - created - as a real teamwork. Although the chapters (and in some cases parts of the chapters) were originally written by one of the two authors, all of them were discussed thoroughly and in detail and have been revised and complemented afterwards. Even if both authors were in agreement on most of the foundational issues discussed in the book, they did not feel it necessary to balance every viewpoint. Thus some individual and personal di?erence or emphasis will still be recognisable from the chapters written by the di?erent authors. In this sense the authors feel speci?cally responsible for the chapters as follows: Mittelstaedt for Chaps. 4, 9. 3, 10, 11. 2, 12, 13 and Weingartner for Chaps. 1, 2, 3, 5, 7, 8. 2, 9. 2, 9. 4. The remaining parts are joint sections. Most of the chapters are formulated as questions and they begin with arguments pro and contra. Then a detailed answer is proposed which contains a systematic discussion of the question. This is the respective main part of the chapter. It sometimes begins with a survey of the problem by giving some important answers to it from history (cf. Chaps. 6 and 9).