Aristotle‘s categories are presented as a system relying on logic and syntax instead of on meanings. His square of oppositions is found to be of crucial importance.

The influence of Spengler on Wittgenstein's philosophical development is considered. The point of interest is in a significant methodological restructuring which it appears to have produced. After an initial over-enthusiastic reception, Wittgenstein is seen to object on some points which he attempted to emend in his own philosophy. Spengler's name disappeared inreworked manuscripts but traces persist in the Philosophical Investigations and an important section (§89-133) is found to be connected with it.

Heidegger's comments about a pair of shoes painted by van Gogh are read with attention to their historical context.

The Five Greatest Kinds discussed in Plato‘s Sophist are taken to be just one instance of a fivefold structure found in various related texts. Contemporary linguistic theories are a source for ideas about its functioning.

The well-known connection between the extant fragments of Philolaus and Plato’s Philebus is examined in its methodological aspect. By drawing on more texts, it is shown that Plato was aware of an explanatory scheme that can be attributed to Pythagoreanism. His attempt to modify it is also outlined, which sets the historical-philosophical perspective.