A Short Philosophical Digression

Physical scientists are not much given to philosophy. They tend to be down-to-earth people, prepared to believe what their senses tell them, and not very concerned about the wider philosophical implications. This reluctance is very clearly seen in the study of heterogeneous catalysis, where the construction of models and the drawing of inferences are exceptionally difficult but vitally important the great variation in the vigour with which these actions are pursued reflects the uncertainty that scientists feel on departing from tangible observations. 

The difficulties attending the extraction of an acceptable conceptual model for a reaction mechanism from experimental findings has been a recurrent theme of the last six chapters. A suggestion as to what needed to be defined before we could say we understood a reaction mechanism was made in Section 5.3 but this was only a start. Since in this chapter and the next the problems of resolving the nature of adsorbed intermediate and their modes of interaction becomes acute, it may be helpful to preface our discussion with a short reflection on exactly what it is we are trying to do, and how far our efforts are likely to meet with success. 

The amount of information needed to start a discussion of mechanism is quite small speculation can then proceed untrammelled by a superfluity of experimental facts. This was often the case with early works on many systems, but not surprisingly as further observations were made the model had to be refined and extended and it became more complicated. More assumptions and suppositions had to be introduced, and more uncertainty entered the conclusions. 

If correct logic is applied, we must suppose that every mechanistic statement is valid within the confines of the theoretical concepts and symbolism available at the time, and the accessible experimental conditions and techniques. The virtuous circle of experiment model - experiment, which is supposed to characterise the scientific method, seems to be followed less often than it might, and 

For nothing worthy proving can be proven Nor yet disproven wher ore be thou wise  

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We start with A short philosophical digression that can be skipped if your interest does not run in that direction. 

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