In examining the sense of predicate we can fmd three import;anttheses in Freges theory: 1.The mode of presentation of referent is contained in the sense of an expression. So, the sense of predicate consists of the mode of presentation of concept as its referent. 2.The sense of predicate is unsaturated. 3.The sense of predicate is part ofthe sense ofthe sentence in which it occurs. In surveying the most important commentarieson the sense of predicate in Freges theory, it was found out that each commentary violates at least one of the above theses. Also, Dummett and Klement give special commentary on unsaturatedness of the sense of predicate, both of interpretations which are inconsistent with The appearence of Ferges theses. It seems, in general, that a proper explanation which will be consistent with all the three theses cannot be given.

In examining the sense of predicate we can find three important theses in Frege’s theory:1- The mode of presentation of referent is contained in the sense of an expression. So, the sense of predicate contains the mode of presentation of concepts, as its referent.2- The sense of predicate is unsaturated.3- The sense of predicate is part of the sense of the sentence in which it occurs.Every given significant commentary for the sense of predicate violates at least one of the above theses. Also, Dummett and Klement give special commentary for unsaturatedness of the sense of predicate, but both of them are inconsistent with what appears from Frege. It seems, in general, that a proper explanation which will be consistent with all three theses cannot be given.

One of the most controversial topics which is discussed by Wittgenstein in Philosophical Investigations is private language argument. According to Wittgenstein, the way in which a language-user categorizes his thoughts, feelings and emotions in the language cannot be talked about personally and privately. Words and Sentences do not gain their meaning in private. Wittgenstein’s argument is based on “correct /seems to be correct” distinction. According to him, if the language-user is authorized to utilize words and sentences privately, the mentioned distinction would be irrelevant and non-sense, normatively speaking. In other words, in such a situation we cannot give an account of the calibration of word use in different contexts. It follows from this that the whole idea of meaning is evaporated. Furthermore, Frege argued in favoure of the objectivity of meaning in his famous article entitled Thought. According to him, the distinction between idea and thought should be taken into account in order to discuss the very idea of ‘meaning’. Idea is entirely private, subjective and associated with mental image, whereas thought is public, objective and associated with meaning. In other words, mental image does not have any role in the formation of meaning, semantically speaking. Frege appealed to Platonic realm in order to give an account of how ideas and meanings can be distinguished from each other, metaphysically speaking. It is said that Wittgenstein is influenced by Fregean account of meaning in formulating his private language argument, although he does not subscribe to Frege’s Platonic ontology.In this article, we are going to give an account of how Fregean account of meaning is utilized in Wittgenstein’s private language argument. Firstly, we formulate and give an account of private language argument in the Wittgensteinian sense. We formulate our argument based on the rule-following argument which has a key role in understanding private language argument. To do so, we try to criticise the anti-realistic account of meaning and justify the realistic account of meaning, according to which the language-user is answerable to patterns of word use. In this way, we can give an account of 'correct /seems to be correct' distinction, semantically speaking. Secondly, we read the private language argument in the light of the realistic account of meaning. Thirdly, Frege’s account of meaning is discussed in details. Finally, Wittgenstein’s private language argument is compared with Fregean account of meaning.

In this essay, we seek to make a comparative overview of the Platonic Form with the main idea of Gottlob Frege in the creation of the Third Realm and to attribute the presence and existence of certain beings, especially thought, to that world. This is, of course, the first study to be carried out, and the main idea is to explore Frege’ s Platonism (meaning its term in contemporary philosophy) in analytic philosophy. Accordingly, the author first examines Plato's original idea of the creation of the universe as well as exemplary beings, then explains Frege's use of the idea and tries to match it. Then, by examining Frege's views on the Third Realm and the creatures present in it, especially thought, we attempt to determine whether a one-to-one correspondence can be established between the two. With the objections and criticisms that the author makes of describing the Frege system in the creation of the Third realm and thought, in the end he claims that the one-to-one correspondence between them cannot be raised. What has been examined as the end result is Frege's overall system and system in Platonism.

In general, there are two current views on the interpretation of the concept of objectivity in Frege. The first view addresses objectivity in the realm of ontology in which the objectivity is independent of everything even human reason. According to this view, one could call Frege’s philosophy a realist philosophy. On the contrary, the second view sees objectivity or the objective in the realm of epistemology, in which the objective is accessible to human reason as an intersubjective thing. Comparing these two views, we would show that every interpretation that regards the objectivity as intersubjectivity would lead to Kant’s transcendental idealism and introduces Frege as a critical philosopher in its Kantian sense. Besides entering theoretical inadequacy in the totality of Ferege’s thought, such an interpretation is incompatible with his philosophy of arithmetic, as, for example, Frege argues that arithmetic as a branch of logic cannot be based on intuition. Accordingly, believing in internal consistency of Frege’s philosophy of arithmetic, we make use of necessary evidence to emphasize on ontological interpretation of the objectivity of thought in his views.

Moral expressivism suggests that 1) moral sentences lack truth conditions and 2) our purpose in asserting moral sentences is to express non-cognitive attitudes such as desires, approval, or disapproval. Moral expressivism meets a fundamental challenge, known as the Frege-Geach problem. Sentences that express moral judgments can form part of semantically complex sentences. “P” (a moral sentence) contradicts “~P”, and “Q” follows logically, by modus ponens, from (1) “P” and (2) “if P, then Q”. Geach argued that noncognitivists are committed to denying that moral predicates mean the same thing in embedded contexts as they do in unembedded sentences (atomic sentences). If “P” does not mean the same as the antecedent of (2), the argument would be invalid. The problem is that the above-mentioned argument is obviously valid. Blackburn has argued that the complex sentence expresses a ‘higher-order’ attitude toward the attitudes expressed by the smaller sentences which make it up. If we accept the premises of a valid argument but deny its conclusion our attitudes clash in the same way that they do if we both believe that P and ~P. Blackburn's meta-attitudes approach faces several problems. Someone who endorses the premises but denies the conclusion of the valid argument commits himself to a moral inconsistency, not a logical one. In addition, uttering both ‘P’ and ‘~P’ seem to be inconsistent but expressivism cannot explain the inconsistency between these two obviously inconsistent sentences. Blackburn's strategy of inventing a new attitude, such as tolerance, is also unable to solve this problem.

The role and importance of natural language in philosophy is clearly significant and obvious. Aristotle for systematizing his logic and formalizing its rules was significantly dependent on ordinary language such that he formulated the rules of his logic in the framework of this language. By criticizing Aristotle’ s logic on the basis of incompetence and limitations of natural language, Frege developed a new philosophical system by introducing a formal language and a new system of logic. Of course these modifications did not end with Frege and continued in later philosophical systems. In this paper, firstly, we consider natural language and it’ s influence on Aristotle’ s logic and the problems of its application in ancient logic. Then some of Frege’ s innovations in formal language and logic will be discussed. After that, we will examine Frege’ s linguistic turn, its turning point, nature and conditions. Finally the effects of formal language in establishing the structure of Frege’ s philosophical system will be considered.

The “Frege-Geach problem” is one of the most challenging problems against the non-cognitivist view. The crisis is rooted in Ayer’s view. While affected by the main thesis of logical positivists –i.e., the verifiability principle, Ayer showed that moral propositions are neither analytic, necessarily true, nor experimental so that their truth rests on reality. He concluded that such propositions are deprived of propositional content and so truth-valueless. His suggested semantics is widely accepted among moral non-cognitivists and today is called ‘nonrepresentational semantics’, one of the negative principles in non-cognitivism. Using the linguistic-logical approach, Searle and Geach, independent from each other, formalized a problem by which non-descriptive semantics for moral judgments fundamentally have undergone criticism. However, this was not the end of the story since the process of responding to the challenge showed that the main source of the problem does not reside in what Geach said, but is rooted in a conspicuous semantics of complex moral judgments in which the moral judgments are embedded. Hence, the problem has confronted a more complicated form, the ‘embedded problem’.

In 1899, David Hilbert offers an articulated axiomatic system for Euclidean geometry and, demonstrating conditionally the meta-theorems of compatibility and independence for this system, proposes a solution to one of the enduring problems of mathematics (known as the problem of parallel lines). Gottlob Frege, the founder of new formal logic, fundamentally disagreed with Hilbert’s formalistic approach and his proofs for the meta-theorems of compatibility and independence. The reasons for the opposition show that Frege’s view on formality of logic and meta-theorems of compatibility and independence is very different from today's point of view. In this paper, after briefly discussing Hilbert’s method in demonstrating meta-theorems of compatibility and independence, and also the main Frege’s objections toward it, I will indicate to Frege’s own method dealing with these issues, and then discuss why eventually mathematicians and logicians, following Hilbert, ignored Frege’s remarks and modern logic, proposing a model theory, stepped on a road which was for Frege a wrong way.

Identity is one of the most important and at the same time controversial topics in Frege’ s writings. In this essay we discuss his account of this subject and try to explain and criticise it’ s different interpretations. Our main question is about the elements that Identity is a relation between them. First of all we explain Frege’ s view of Identity in “ Begriffsschrift” (Conceptual Notation). The last considerations of Frege about this subject are represented in another well known work of him which is called “ Ü ber Sinn und Bedeutung” (On Sense and Reference), therefore in the next section we examine the concept of identity in this essay. The aim of this essay is not criticizing the view of Frege, but primarily to understand it, because that is the only way that we can grasp crucial issues like the essence of number in “ Die Grundlagen der Arithmetik” (Foundations of Mathematics) and Russell’ s paradoxes concerning the fifth axiom of “ Grundgesetze der Arithmetik” (Basic Laws of Arithmetic).