A model is given of the development of a radialised larval head pattern inLimnaea stagnalis, as it occurs under certain experimental conditions. It is assumed that the differentiation of the pattern is entirely based on cell-internal factors, and that the internal state of each cell is dependent on that of its progenitor and on the direction of the division by which it is produced. This internal state determines the direction of the subsequent division or the nature of the cell's differentiation. (...) Cell interactions, which are during this period of minor importance, are left out of consideration. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:HUME, THE CAUSAL PRINCIPLE, AN'D KEMP SMITH When we say of a proposition that it is possible, we sometimes mean no more than that it is logically possible, that is, consistent with itself. A proposition can be possible in stronger senses than this, but not in any weaker one. For a sense of "p is possible" that did not entail "p is self-consistent, "would have to be a sense (...) of "p is possible" which was consistent with "p is self-inconsistent" And it is obvious that there can be no such sense as that. One of the stronger senses in which a proposition can be possible is this: consistent (with itself and in addition) with every observation-statement. (I mean by an observationstatement, a proposition which, if it were true, could in principle be discovered by experience to be true.) If a proposition? is contingent, (that is, neither necessarily true??t necessarily false), then its negation (its contradictory) not-p is contingent too; and since contingent, not necessarily false; and since not necessarily false, consistent with itself. So, given any contingent propositions, its falsity is among those propositions which are possible in the first and weak sense mentioned above. If a proposition? is not only contingent but unverifiable,(that is, not deducible from any observation- statement), then not-p is consistent both with itself and with every observation -statement. So, given any unverifiable contingent proposition, its falsity is among those propositions which are possible in the second and stronger sense mentioned above. Some stock examples. "Whatever is a raven is black" is contingent, and its falsity therefore possible in the first sense; so too is its contradictory "There are such things as non-black ravens" contingent, and its falsity possible in the first sense. But the latter proposition is not unverifiable, since there are observation-statements from which it is deducible. ("There are such things as green ravens", for example; or "A green raven was in captivity at Taronga Park Zoo in January 31st 1975".) The former proposition, on the other hand, is not only contingent but unverifiable; since there are no observation -statements from which it is deducible. Hence, "whatever is a raven is black" is a proposition the falsity of which is possible both in the first and in the second sense noticed above. A third and still stronger sense in which a proposition can be possible is the following:? is possible if and only if (p is consistent with itself,every observation-statement is consistent with p, and in addition)? is neither more nor less probable in relation to the conjunction of e and n, where e is any observation-statement and? any necessary truth, than it is in relation to? alone. The last condition may be expressed, symbolically, as "P(p/n.e) » P(p/n) for all necessarily true? and all observation-statements e"; or in Carnap' s phrase as, "every observation- statement is initially irrelevant to p." Some examples will quickly make the idea of initial irrelevance, and its opposite, more familiar; and hence will make the third sense of "p is possible" more familiar. Let? be any necessary truth and e any observation-statement. Now let? be, for- example,some necessarily false proposition; then, since P(p/n) « o = P(p/n.e), e is initially irrelevant to p. Or let? be necessarily true; then, since P(p/n) ¦ 1 = P(p/n.e), e is again initially irrelevant to p. Again, let? be "Whatever is a raven is black": then some observation- statements e are initially relevant to p. For if e is "This raven is black," for example, P(p/n.e)>P(p/n) ; or at any rate, that is what we think if we are not inductive sceptic?. Again, if? is "The Holy Ghost proceeds from the Father and the Son", it is at least very plausible to say that every observational e is initially irrelevant to p; since there appears to be no observational e such that P(p/n.e)>P(p/n), or P(p/n.e). (shrink)

A careful and competent introduction to the Russell-Broad type of analytic philosophy.--A. C. P.

Messages describing life after death from the author's deceased brother-in-law.--A. C. P.

The notion that our society, its education system and its intellectual life, is characterised by a split between two cultures – the arts or humanities on one hand and the sciences on the other – has a long history. But it was C. P. Snow's Rede lecture of 1959 that brought it to prominence and began a public debate that is still raging in the media today. This fiftieth anniversary printing of The Two Cultures and its successor piece, A Second (...) Look features an introduction by Stefan Collini, charting the history and context of the debate, its implications and its afterlife. The importance of science and technology in policy run largely by non-scientists, the future for education and research, and the problem of fragmentation threatening hopes for a common culture are just some of the subjects discussed. (shrink)

C P Ormell; Ideology and the Reform of School Mathematics, Journal of Philosophy of Education, Volume 3, Issue 1, 30 May 2006, Pages 37–54, https://doi.org/10.1.

In an influential article, Anthony Kenny charged that (a) the view of freedom in Descartes’ “1645 letter to Mesland” is incoherent, and (b) that this incoherence was present in Descartes’ thought from the beginning. Against (b), I argue that such incoherence would rather support Gilson’s suspicions that the 1645 letter is dishonest. Against (a), I offer a close reading of the letter, showing that Kenny’s objection seems plausible only if we misconstrue a key ambiguity in the text. I close by (...) defending Descartes against some related worries of my own about the degrees of Cartesian freedom. I conclude that there is really no good reason to deny that Descartes’ view in the 1645 letter is both internally coherent and a genuine explication of the Meditations’ account of freedom. (shrink)

In the Fourth Meditation, Descartes asks: 'If God is no deceiver, why do we sometimes err?' Descartes's answer (despite initial appearances) is both systematic and necessary for his epistemological project. Two atheistic arguments from error purport to show that reason both proves and disproves God's existence. Descartes must block them to escape scepticism. He offers a mixed theodicy: the value of free will justifies God in allowing our actual errors, and the perfection of the universe may justify God in making (...) us able to err. Though internally coherent, Descartes's theodicy conflicts with his view of divine providence. (shrink)

Hsiao has recently developed what he considers a ‘simple and straightforward’ argument for the moral permissibility of corporal punishment. In this article we argue that Hsiao's argument is seriously flawed for at least two reasons. Specifically, we argue that a key premise of Hsiao's argument is question-begging, and Hsiao's argument depends upon a pair of false underlying assumptions, namely, the assumption that children are moral agents, and the assumption that all forms of wrongdoing demand retribution.

We formalise the notion of those infinite binary sequences z that admit a single program P which expresses the entire algorithmical structure of z. Such a program P minimizes the information which must be used in a relative computation for z. We propose two concepts with different strength for this notion, the learnable and the super-learnable sequences. We establish three different equivalent characterizations of learnable (super-learnable, resp.) sequences. In particular, we prove that a sequences z is learnable (super-learnable, resp.) if (...) and only if there is a computable probability measure p such that p is Schnorr (Martin-Lof, resp.) p-random. There is a recursively enumerable sequence which is not learnable. The learnable sequences are invariant with respect to all total and effective transformations of infinite binary sequences. (shrink)