Various formulations of the principle of simplicity in science are examined and rejected in favor of Goodman's proposal, the essence of which is to concentrate attention upon the predicates that form the extralogical basis of any given theory and to provide measures for comparing the relative structural simplicity of different sets of such predicates. The postulational basis of Goodman's method is set out and explained, together with some important amendments and additions, and a number of theorems are proved, with whose aid the simplest theory to account for a certain corpus of scientific phenomena is readily determinable.

Theoretical problems concerning concepts of systems and measurement of behavior were encountered during experimental studies of the effects of electrical stimulation of the brain on the social behavior of a monkey colony. General problems involved in the description and measurement of behavior of natural systems, and especially of organisms are discussed.

In animals with differentiated brain the general process of stimulation may be divided into four subprocesses: input, throughput, transput and output.

Categories of behavior, temporal and spatial units, and logical rules of homogeneity for sorting data and comparing measurements and categories, are discussed. Simple behavioral units are divided into: 1. Individual a. static or postural b. dynamic or gestural 2. Social a. static b. dynamic. Complex behavior is divided into: 1. Simultaneous 2. Sequential 3. Syntactic 4. Roles.

The process of interpretation of data by the observer is assumed to be dependent upon actual behavior of the system, techniques of observation and experimentation, theoretical and technical processes of analysis, and synthesis and integration of data. Expression of behavior in mathematical terms insures greater accuracy than descriptive methods and enables data to be processed with computers.

The Lorentz-formulae are deduced from three factual statements the physical meaning of which is explained in terms of operations with clocks, light-signals and measuring rods. These statements are:

(1) The time-length of a process is invariant.

(2) The velocity of light is the same in all inertial systems.

(3) The velocity of light is independent of the source.

It is also shown that these statements can be deduced from the Lorentz-formulae. They are the physical content of the latter.

The principle of relativity and the light-principle together, however, contain more physical meaning than the Lorentz-formulae.

Operational definitions are given for all relevant concepts.

Much of the Mill-Whewell dispute was purely verbal, but much was not. Mill did not understand Whewell; the true character of the non-verbal aspect of the controversy emerges only upon adequate analysis of Whewell's actual position. Such analysis shows that Mill's objections to Whewell were misdirected, although suggestive of other which might, if prosecuted, carry. Ultimately, the dispute has to do with the given; neither man gives an adequate account of it. For this reason, the controversy cannot be resolved definitively in favor of either of them.

The notion that there is a category mistake or some other conceptual confusion in regarding seeing, hearing, and other forms of perception as events, states, or processes is incorrect. Ryle's analysis of “seeing” as an achievement word does not rule out our regarding seeing as an event, but in fact suggests that we do so when we carry the analysis beyond the point where Ryle leaves it. Furthermore there are uses of “see” not noticed by Ryle which justify our saying that within certain contexts seeing is a state and within other contexts a process. The question of what these events, states, and processes are cannot be met without recognizing a fundamental duality of aspect that characterizes perception. This duality can be formulated in terms of the way perception is known. One who observes a perceiver knows the perceiver's perception in a categorically different way than the perceiver knows it. From this it can be seen that perceptual events, states, and processes have both a physical aspect and an epistemological aspect. Any attempt to reduce one of these aspects to the other would involve a category mistake.