Bundel essays over aspecten van het denken van de Duitse filosoof Martin Heidegger (1889-1976).

We consider the problem of whether there are deterministic theories describing the evolution of an individual physical system in terms of the definite trajectories of its constituent particles and which stay in the same relation to quantum mechanics as Bohmian mechanics but which differ from the latter for what concerns the trajectories followed by the particles. Obviously, one has to impose on the hypothetical alternative theory precise physical requirements. We analyze various such constraints and we show step by step how (...) to meet them. This way of attacking the problem turns out to be useful also from a pedagogical point of view since it allows one to recall and focus on some relevant features of Bohm's theory. One of the central requirements we impose on the models we are going to analyze has to do with their transformation properties under the transformation of the extended Galilei group. In a context like the one we are interested in, one can put forward various requests that we refer to as physical and genuine covariance and invariance. Other fundamental requests are that the theory allows the description of isolated physical systems as well as that it leads to a solution (in the same sense as Bohmian mechanics) of the measurement problem. We show that, even when all the above conditions are taken into account, there are infinitely many inequivalent (from the point of view of the trajectories) bohmian-like theories reproducing the predictions of quantum mechanics. This raises some interesting questions about the meaning of Bohmian mechanics. (shrink)

In this paper I shall venture into an area with which I am not very familiar and in which I feel far from confident; namely into phenomenology. My main motive is not to get away from standard, boring, methodological questions like those of induction and demarcation; but the conviction that a phenomenological account of the empirical basis forms a necessary complement to Popper's falsificationism. According to the latter, a scientific theory is a synthetic and universal, hence unverifiable proposition. In fact, (...) in order to be technologically useful, a scientific hypothesis must refer to future states-of-affairs; it ought therefore to remain unverified. But in order to be empirical, a theory must bear some kind of relation to factual statements. According to Popper, such a relation can only be one of potential conflict. Thus a theory T will be termed scientific if and only if T is logically incompatible with a so-called basic statement b, where b is both empirically verifiable and empirically falsifiable. In other words: T is scientific if it entails ¬b; where b, hence also ¬b, is an empirically decidable proposition. (shrink)

Domestic livestock animals and soils must be considered together as part of an agroecosystem which includes plants. Soil sustainability may be simply defined as the maintenance of soil productivity for future generations. There are both positive and negative aspects concerning the role of animals in soil sustainability. In a positive sense, agroecosystems which include ruminant animals often also include hay forage-or pasture-based crops in the humid regions. Such crops stabilize the soil by decreasing erosion, improving soil structure and usually require (...) fewer chemical inputs. Monogastric animal culture is based on an agroecosystem consisting of mainly grain crops. These crops can result in the soil being exposed to water and wind erosion although soil conservation practices that significantly reduce soil losses may be followed. The management of animal manures is not always compatible with soil conservation practices. Careful management of the nutrients in manure is absolutely necessary to avoid nitrate contamination of ground water or phosphorus loading of streams and lakes. In a negative sense, increases in animal livestock populations in association with human population growth are promoting desertification in the arid and semi-arid regions of the world. The key component for a fully compatible and acceptable association between domestic animals and soil productivity is proper management. Careful management of the components of an animal-based agroecosystem is required if soil productivity and environmental quality are to be maintained. Although we have much to learn, technologies are available to move a considerable way towards this ideal state. (shrink)

Domestic livestock animals and soils must be considered together as part of an agroecosystem which includes plants. Soil sustainability may be simply defined as the maintenance of soil productivity for future generations. There are both positive and negative aspects concerning the role of animals in soil sustainability. In a positive sense, agroecosystems which include ruminant animals often also include hay forage-or pasture-based crops in the humid regions. Such crops stabilize the soil by decreasing erosion, improving soil structure and usually require (...) fewer chemical inputs. Monogastric animal culture is based on an agroecosystem consisting of mainly grain crops. These crops can result in the soil being exposed to water and wind erosion although soil conservation practices that significantly reduce soil losses may be followed. The management of animal manures is not always compatible with soil conservation practices. Careful management of the nutrients in manure is absolutely necessary to avoid nitrate contamination of ground water or phosphorus loading of streams and lakes. In a negative sense, increases in animal livestock populations in association with human population growth are promoting desertification in the arid and semi-arid regions of the world. The key component for a fully compatible and acceptable association between domestic animals and soil productivity is proper management. Careful management of the components of an animal-based agroecosystem is required if soil productivity and environmental quality are to be maintained. Although we have much to learn, technologies are available to move a considerable way towards this ideal state. (shrink)

We discuss a generalization of the standard notion of probability space and show that the emerging framework, to be called operational probability theory, can be considered as underlying quantal theories. The proposed framework makes special reference to the convex structure of states and to a family of observables which is wider than the familiar set of random variables: it appears as an alternative to the known algebraic approach to quantum probability.

We study the possibility of representing the proposition lattice associated with a quantum system by a linear vector space with coefficients from ap-adic field. We find inconsistencies if the lattice is assumed, as usual, to be irreducible, complete, orthocomplemented, atomic, and weakly modular.

The probability pattern emerging in two-slit experiments is a typical quantum feature whose essential ingredients are examined by translating them into the spin- $ \frac{1}{2} $ formalism. In view of the existence of extensions of quantum theory preserving some classical structure, we discuss how the two-slit probabilities behave under such extensions. We consider a generalization of the standard classical probability theory, to be called operational probability theory, that turns out to host the so called quantum probabilities.