Sakineh Karimi

Presentists argue that only present entities exist absolutely and unrestrictedly. Presentism, which itself is a temporal analog of the modal doctrine of actualism, is an ontological idea about time and existence against theories such as eternalism, possibilism, and growing block theory. Thus, presentists deny the existence of atemporal or timeless entities and describe presentism as a version of the (A-theory), which makes a difference between present, past, and future. Also, presentists are not able to ontologically, justify the existence of some entities such as Socrates and the year 3000 in the past and the future and the relations involving non-present objects like ‘Abraham Lincoln was taller than Napoleon Bonaparte’. However, presentism is altered via the addition of an abstract four-dimensional manifold of ersatz time, which is a type of (B-theory) series, to identify all ontological entities and justify the dynamic world. This inquiry is an attempt to put a completely different perspective on presentism and, the result obtained that despite the new conceptualization of time, there is an inconsistency between time and being in presentism. Therefore, presentists have failed to determine the ontological identification of cross-temporal relations, reference and propositions, and truth-makers. Also, whatever the final outcome of the debate between presentism and other views is significantly eternalism, according to ersatz presentism, it is hard to make sense of the idea that things change from one moment to the next.

Reflecting on Avicenna’s works indicates that by ‘Dhat’(ذات), when used in the context of universal essences, he means either the quiddity or the nature, and when used in the context of individual essence, especially God’s essence, he means the very existence. The second meaning, i.e. the nature, which is the result of his inquiry about the reality of things, is based on the first one, i.e. the quiddity. According to this second meaning, and througha kind of thought experiment and using human mind’s capacity, Avicenna discusses different aspects of essence and their implications in various sciences. These conceptual analyses help us discover his idea of essentialism. The final conclusion is that Avicenna’s essentialism is consistent with his idea about existence and the definitions can refer to the essence of objects.

Abstract In the light of the analysis of Avicenna’s definition of “nature” we can discover the main principles of his physics, which are: ‘The agency of the nature’, ‘the directness of this agency’, ‘the natural object’, and ‘the essential agency of the nature’. One of the main consequences of this analysis is that the nature could be considered as the direct cause of the motion, immobility and spatial balance of the material objects. Moreover, it shows that natural objects are essentially capable of possess natural properties. Accordingly, Avicenna considers that the natural properties are the same as the essential properties, which material objects have them necessarily.

The problem of natural kind is considered to be a complicated problem in philosophy as it is linked to the problem of essence on the one hand and the problem of individuals on the other. While nominalists refuse to accept universals in their ontology, realists believe in natural kinds and endeavor to justify classification of things by appealing to existence of natural kinds and their essential properties. In the first part of this paper we briefly survey two kinds of criteria for being a natural kind. In the second part we will evaluated the proposed criteria. Finally we conclude by the following six criteria: Reality and absoluteness, possessing of full essence, hierarchy, changelessness, categorization and contribution to identical theory.

In some cases, Avicenna used the semantical premises in order to deduce some conclusions in his Physics. For instance, he analyzes five derivatives of the word “tabiat” and then in the light of these analyses, he concludes that the natural properties of an object are caused by its essence and are based on it. Here, the major problem is how to justify Avicenna's passage from semantical premises to physical consequents. This paper shows that through analyzing the relation between nature and its derivatives, on one hand, and explicating Avicenna’s definition of the “nature” on the other hand, we can defend the rationality of such a passage.