The doctrine that the content of the conclusion of a deductively valid argument is included in the content of its premises, taken jointly, is a familiar one. It has important consequences for the question of what value valid arguments possess, since it indicates the poverty of three traditional answers: that arguments may and should be used as instruments of persuasion, that they may and should be used as instruments of justification; and that they may and should be used to advance knowledge. The truth is, however, that in each of these cases the argument has only a managerial role and, if there is any work done, it is the premises that do it. It will be maintained that this point has little force against the critical rationalist answer, which I shall defend, that the principal purpose of deductive reasoning from an assemblage of premises is the exploration of their content, facilitating their criticism and rejection. That said, the main aim of the present paper is not to promote critical rationalism but to consider some published objections to the doctrine that a statement asserts every statement that is validly deducible from it. The alleged counterexamples to be considered fall roughly into two groups: statements that emerge with time from a rich mathematical or empirical theory, but were originally unformulated and are deducible from the theory only in a non-trivial way (Frederick 2011, 2014; Williamson 2012); and statements, notably disjunctions, that are easily formulated and are deducible from a theory in a trivial way (Schurz & Weingartner 1987; Mura 1990, 2008; Gemes 1994; Yablo 2014). Each of these counterexamples will be evaluated and dismissed.

In The Organon, the fallacy of begging the question first appears in the fifth chapter of “the sophisticated refutations, ” where Aristotle believes that this fallacy is deceptive only when similar things cannot be distinguished from different things. On this definition, begging the question is a circular arguments, in which the conclusion is identically one of the premises. The same interpretation appears in the works of Muslim logicians as well, where most examples are those in which the conclusion and premises differ only in their appearance. In the classical logic, however, reiteration of premises in the conclusion does not amount to the invalidity of the argument. In the present research, which is done with the analytical-analogical method, we propose a structure of the fallacy of begging the question: it does not involve a simple circle where the conclusion appears in the premises,rather, it involves the claim that the circular relation between the premise and the conclusion is a criterion for the truth of a certain proposition. In fact, the formal structure of this fallacy is as follows: (P→, P)├,P. Given the truth or falsity of a proposition for an audience, this proposal can explain why certain circles are epistemically misleading to the audience, and others are not. Moreover, the argument “if P, then P” will not be rendered invalid in this way neither syntactically nor semantically.

Cosmological argument is a general name that includes many different arguments, but all of its versions are a posteriori (contrary to ontological argument) and based on an apparently common feature of our experience (contrary to argument from design). I try to explain the structure of the cosmological argument via explaining some of its important versions. In this regard, Aquinas versions of cosmological argument; the arguments from motion, causation and contingency (the first three ways of his famous five ways) are discussed in details. Then I proceed to discuss Kalam cosmological argument, which is rooted in Islamic theological writings in cosmological argument, which is rooted in Islamic theological writings in the Middle Ages, and the argument from the principle of sufficient reason, respectively. Criticizing all of these versions, I conclude my paper by explaining and defending Avicenna"s version of cosmological argument.

The argument from illusion and the argument from hallucination refute the directness of visual perceptual experience. Although the first argument includes at least two disputable premises (the phenomenal principle and the common kind assumption), the second one just includes the common kind assumption. I will illustrate that the arguments, not only have different premises, but concern different subjects. The argument from illusion concerns the object of visual perceptual experience, but the argument from hallucination concerns the nature of the experience. On the basis of this consideration, I will propose the two different senses of directness. According to the first sense, an experience is direct, if it is directed to the world itself. But according to the second sense, an experience is direct, if the world itself, notably not its representation, constitutes the experience.

In 1970, Gödel showed his ontological argument to Dana Scott and discussed it with him. Afterwards, Scott presented a slightly different version of the argument at Princeton University. The logical system of the argument is a second-order quantified S5-modal logic with identity and an abstraction operator. Granted the acceptability of the underlying logical system, Godels conclusion that necessarily there exists a God-like being) can be derived from the premises-with Godel and Scott on the scene, who can say otherwise? Sobel, however, proved that the system faces modal collapse-i.e. P↔ðP is derivable from the system. Responding to Sobel, Anderson tried to block this by weakening some axioms and definitions.In this paper, I will be trying to consider Godels ontological argument (Scotts version) from a logical point of view, along with Sobels criticism and Andersons emendations.

The most important topic in logic is deduction which is treated in logical books under the heading of argument. Ancients divided argument into the three classes of syllogism, induction and analogy.As to kinds of and the sort of division of argument some questions has been raised. On the one hand, besides the theory of syllogism which is without doubt Aristotle's masterpiece one of important works of Aristotle's in the field of logic is the topic of "conversion", "contradiction" and "contrast".Of course, in Organon these topics have been treated incidentally. Ibn Sina added some relations to those which Aristotle had introduced and by finding the similarity of these topics brought them together in his logical works.After Ibn sina, logicians by following him introduced these relations under the heading "representative argument". The same topic has been treated in recent books of traditional logic with the title "rules of proposition". This title suggests that these logicians regard "rules of proposition" as a kind of deduction and argument.In this article the author defends the latter view and by assuming the conversion to be a kind of argument and examples like that has proposed a division of deduction in which the place of these arguments has been clearly defined and has no difficulties of previous division.

In the past the Majority of philosophers believed that in the process of perception one is aware of some thing, called sense- datum, which is other than the physical object itself. But today, the majority of philosophers, specially the analytic philosophers deny that one needs to postulate such entities and affirm that we are normally: and directly aware of the external world. In this research, using an argument called "argument from illusion", it is argued that sense- datum theory is correct and that we are not directly aware of the external world.