We begin by examining the type of theoretical indefiniteness in physics which is due to our partial, subjective lack of knowledge of the properties of individual particles within large systems. Historically, this problem was first treated in the latter part of the 19th century. At that time, thermodynamics was enjoying great success; it had developed empirically from the treatment of heat engines and the study of chemical reactions. It could successfully describe macroscopic phenomena, for example the rise in pressure in a steam boiler when its temperature is increased.