Witold Marciszewski

Zwrot \"Mathesis Universalis\" (MU) oznacza projekt unifikacji całości wiedzy za pomocą metody matematycznej. Powstał on pod tą nazwą u progu nowożytności, a częściowo miał antycypacje w starożytności i średniowieczu. Głównymi jego rzecznikami byli Kartezjusz i Leibniz. Podejście Leibniza jest radykalnie formalistyczne, a przez to nadające sie do realizacji maszynowej, podczas gdy Kartezjusza - zdecydowanie antyformalistyczne. Artykuł koncentruje się na projekcie Leibniza jako tym, który ma kontynuację w nauce współczesnej. Zamysł, żeby narzędziem realizacji projektu była uniwersalna symbolika i rachunek logiczny jest obecnie realizowany w odniesieniu do całości matematyki za pomocą środków, które jako pierwszy stworzył Gottlob Frege (1879). Istotny wkład ma Georg Cantor jako autor teorii mocy zbiorów, która wprowadza odróżnienie zbioru nieskończonego przeliczalnie od zbioru o mocy kontinuum. Umożliwia to dowód fundamentalnego dla współczesnej MU twierdzenia o istnieniu problemów nierozstrzygalnych w arytmetyce, co jest dziełem Kurta Gödla, oraz w logice. To drugie wykazał Alan Turing, dowodząc, że zbiór realizowalnych przez maszynę programów do dokonywania obliczeń, czyli do rozstrzygania problemu, jaka jest wartość określonej funkcji, jest tylko przeliczalny, podczas gdy zbiór problemów do rozstrzygnięcia ma moc kontinuum; stąd wynika, że pewne problemy są nierozstrzygalne w sposób formalny czyli maszynowy, co z kolei implikuje nierozstzygalność logiki. Analogiczny wynik Gödla ma ważne dopełnienie w jego twierdzeniu, że ograniczenia rozstrzygalności są tylko względne (w stosunku do określonego systemu formalnego) i mogą być przezwyciężane przez konstrukcję nowych pojęć pierwotnych, aksjomatów i metod postępowania badawczego. Rysuje się więc przed nauką możliwość nieustannego postępu. Takie dynamiczne ujęcie stanowi rys istotnie różniący współczesną postać MU od klasycznej, którą cechowała statyczność

1. STRUCTURE AND REFERENCES 1.1. The main part of the dictionary consists of alphabetically arranged articles concerned with basic logical theories and some other selected topics. Within each article a set of concepts is defined in their mutual relations. This way of defining concepts in the context of a theory provides better understand ing of ideas than that provided by isolated short defmitions. A disadvantage of this method is that it takes more time to look something up inside an extensive article. To reduce this disadvantage the following measures have been adopted. Each article is divided into numbered sections, the numbers, in boldface type, being addresses to which we refer. Those sections of larger articles which are divided at the first level, i.e. numbered with single numerals, have titles. Main sections are further subdivided, the subsections being numbered by numerals added to the main section number, e.g. I, 1.1, 1.2,..., 1.1.1, 1.1.2, and so on. A comprehensive subject index is supplied together with a glossary. The aim of the latter is to provide, if possible, short defmitions which sometimes may prove sufficient. As to the use of the glossary, see the comment preceding it.

The paper is meant as a survey of issues in computational complexity from the standpoint of its relevance to social research. Moreover, the threads are hinted at that lead to computer science from mathematical logic and from philosophical questions about the limits and the power both of mathematics and the human mind. Especially, the paper addresses Turing's idea of oracle, considering its impact on computational (i.e., relying on simulations) economy, sociology etc. Oracle is meant as a device capable of finding the values of uncomputable functions. Such an idealized entity is exemplified by the human mind's procedure of recognizing the truth of the Gödelian sentence, of identifying uncomputable numbers through Turing's diagonal procedure, etc. Since such procedures are strictly defined and are as reliable as any calculations, they are worth to be called computation as well. From the computation in the strict sense, that defined as purely algorithmic (mechanical) process, one distinguishes them with the term "hipercomputation". Now the following questions arise. - Are there undecidable problems (ie. not decidable with appropriate algorithms) in social research as are (according to what is reported esp. By S. Wolfram) in natural sciences? The answer in the negative would impose limitations on computer simulations (as entirely relying on algorithms). - If there are, then we have the next question: can such problems be addressed with hipercomputational procedures? - How such hipercomputational procedures would be related to analog computation (coextensive, everlappiing, etc.)? Another set of issues is stated in terms of tractability of decidable problems, that is, the efficiency of algorithms needed for solutions. As inefficient are regarded those which require more resources (time, memory, etc.) than is available in a foreseeable future. In this context, one discusses methods of such an efficient organizing computational processes to overcome the scarcity of resources; thus parallel, distributive, interactive, etc. computing are used as remedies. The paper claims, hinting at F.Hayek's ideas, that in some social systems (e.g., stock exchange, and free market in general) such an efficient organization of their computational activities spontaneously evolves. And this is the main source of its advantages over the central economic planning (as defended by O. Lange). This noticing (in terms of complexity theory) of analogy between Hayek's point and the current discussion of efficiency of algorithms is what may count as an original contribution of the present paper

We discuss the existence of universal spaces (either in the sense of embeddings or continuous images) for some classes of scattered Eberlein compacta. Given a cardinal κ, we consider the class Sκ of all scattered Eberlein compact spaces K of weight ≤ κ and such that the second Cantor-Bendixson derivative of K is a singleton. We prove that if κ is an uncountable cardinal such that κ = 2&ltκ, then there exists a space X in Sκ such that every member of Sκ is homeomorphic to a retract of X. We show that it is consistent that there does not exist a universal space (either by embeddings or by mappings onto) in Sω₁. Assuming that ∂ = ω₁, we prove that there exists a space X ∈ Sω₁, which is universal in the sense of embeddings. We also show that it is consistent that there exists a space X ∈ Sω₁, universal in the sense of embeddings, but Sω₁ does not contain an universal element in the sense of mappings onto

When discussing Kazimierz Ajdukiewicz's role in philosophy, it is worthwhile recalling his participation in scholarly controversies. It was characteristic of his open mind that his taking part in debates was motivated by a vivid interest in various ways of thinking. Ajdukiewicz's intellectual power consisted, so to speak, in his ability of not to understand. This ability has brought him success in some important debates, concerning i.a. the classical logical concept of contradiction and the debate on universals raised in modern Poland with the nominalistic program of Stanislaw Lesniewski and Tadeusz Kotarbiński. In this latter debate Ajdukiewicz shows that when one says that individuals exist, the word „exist" refers to something different that in the statement that universals exist. In other words, the functor „is" has a different category in the definition of an individual from that appearing in the definition of a universal; hence there must be two different senses of the word „exist"