Categorical and ConditionalDeduction and Inductionofthe Natural, Temporal, Extensional and Logical Modalities.

The science of Logic stands at the interface between the two main branches of Philosophy, namely Epistemology (the study of knowing) and Ontology (the study of being). Its task is to determine precisely the way people can and do get to know the world around them. Its role is both descriptive and prescriptive. Its means include: observation of common thought-processes and everyday language, analysis of recurring patterns and components, and evaluation with reference to rational and empirical criteria. Logic is thus a study of form, irrespective of content.

Future Logicis an original, wide-ranging, profound and timeless treatise of formal logic, intended for both the uninitiated and the specialist.

What do we mean when we say that something is ‘necessarily’, ‘actually’ or ‘possibly’ so and so? These so-called ‘modalities’ are attributes of relations, and they vary in meaning. For each category of modality (like necessity or possibility), there are several types of modality (the natural, the temporal, the extensional, the logical, and others), and each of these modalities serves a distinct purpose, expressing some aspect of reality or the state of our knowledge about it. Each category and type of modality has its own peculiar logical properties, and a host of relations to the various others.

Future Logicdemonstrates the centrality of modal concepts in human knowledge and in the processes leading to it. Starting with precise definitions of the various categories and types of modality, it develops a systematic study of reasoning processes involving them, which not only retraces past achievements in the field but also enables a great many new discoveries.

Modality is significant not only in the study of categorical propositions, but also in that of conditional propositions. There are as many forms of conditioning as there are categories and types of modality; and while some of their logical properties are similar, many are quite different. What this means in practise, is that we cannot reason properly without awareness of these differences. The study of conditioning is of fundamental importance to an understanding of causal relations.

Future Logicisthe first work everto develop a thorough formal study of the natural, temporal and extensional types of conditioning(as well as logical conditioning), including their production from modal categorical premises.

Our knowledge of things is of very variable certainty: some of it seems solidly established almost immediately and forever, some of it requires a lot of work to acquire and seems tentative and open to revision. This observation suggests a distinction between ‘deductive’ and ‘inductive’ logic. Each of these fields comprises a multitude of specific processes, which require detailed investigation. While deductive processes have traditionally received much attention, logicians have done little formal work in relation to inductive processes, apart from the crucial and relatively recent elucidation of adduction (the processes of confirmation or elimination of hypotheses).

Future Logicisthe first work everto strictly formalize the inductive processes of generalization and particularization, through the novel methods of factorial analysis, factor selection and formula revision.

Science (i.e. the special sciences) and logical philosophy have throughout history fed off each other. The practises of scientists have often caused theoretical reflections by logicians; indeed, many scientists were themselves logicians. Likewise, the methodological principles clarified by logicians have often facilitated and improved the work of scientists.

Future Logic is a revision of the ‘scientific method’, challenging scientists with new, more rigorous methodological standards, but also providing them with finer cognitive tools likely to greatly enrich science. (Hence, the book’s title.)

© Avi Sion, 1990 (Rev. ed. 1996).