 I think you have understood the first part of the unit that is Nassar of formal logic. The main parts of the first part that is what is logic, what is formal logic and what is the relation between logic and the deductive argument. But their learners in the part 2 in the same unit that is Nassar of formal logic that is symbolic logic a kind of formal logic. Their learners modern logic or symbolic logic is a formal logic. Symbolic logic is a developed form of Aristotelian logic. The difference between symbolic logic and Aristotelian logic is not a difference of kind by a difference of degree. Their learners symbolic logic makes an extensive use of symbols apart from variables like small letters P, Q, R, S, T etcetera. Symbolic logic makes use of certain signs or symbols such as negation, dot, fail, implication and bioconditional that is known as logical constants. Propositional calculus is a basic part of logic and is usually taken as starting point or the study of symbolic logic. Propositions are taken as basic units and in propositional logic propositions are not divided into component parts. Their learners in propositional calculus the letters of the alphabet like small letter that P, Q, R, S, T and so on stand for propositions and these letters as used in propositional calculus are known as propositional variables because they can stand indifferently for any proposition. Their learners you take example that is the sentence it is raining now is a proposition because this sentence can be either true or false. A proposition is defined as any sentence which is either true or false but cannot be bought true and false at the same time. The sentence like the first one today is a holiday and the second sky is blue and arsenic is poisonous that is number three are all propositions. These three propositions cannot be symbolized as one, two and three etcetera which are known as propositional variables. Their learners words like not and or if then etcetera are known as logical constants and these logical constants are represented by artificial symbols in the following way for not P we write negation P for P and Q we write P dot Q for P or Q we write P value for if P then Q we write P implies Q. Their learners thus in propositional logic we symbolize the compound propositions by means of variables and constants. Thus in symbolic logic compound propositions are symbolized by means of variables and constants. The P dot Q P value Q P implies Q negation P are called truth functions because the truth and falsity of these propositions or functions depend on the truth and falsity of the constituent variables like P and Q. This P dot Q P value Q P implies Q negation P are logical forms of different compound propositions. Thus we can speak of the logical form of a statement or set of statements constituting an argument and in doing so we distinguish the form or structure of statements or argument from its subject matter. Now you have to know a very basic concept that is logical form and matter. Two or more arguments may have different subject matter but all of them may share the same form. For example the following two arguments have different subject matter but have the same form. Now their learners you take the first example that is if it rains the ground is wet and it rains therefore the ground is wet. Now their learners this is the first example and the second example you can take that is if a joy wins the game then his mother is happy and the second one if a joy wins the game therefore his mother is happy. This is the second example. Now their learners how can we symbolize the two arguments. Now you see these two arguments have different subject matter but they share the same logical form that is p implies q and p therefore q. Their learners this argument form is valid therefore all arguments that share this form this form is what p implies q and p therefore q. This logical form will be valid no matter what their subject matters are. Thus the special symbols of modern logic help us to exhibit with greater clarity the logical structure or forms of propositions and argument. Thus symbolic logic as a formal logic is called concerned with validity or invalidity of particular individual arguments. Symbolic logic offers methods of deciding the validity or types of argument. Symbolic logic or formal logic is the study of symbolic abstractions of the formal logic research of logical inferences. Their learners the different systems of formal logic, truth functional system, axiom system, quantification system, model theory, set theory or Boolean algebra of classes are abstract study of propositions and of deductive arguments. Set theory or Boolean algebra of classes is also known as mathematical logic and as such it is purely a formal study. Thus their learners formal logic is the abstract study of propositions and of deductive arguments. It is not an empirical study at all as such it is not concerned with empirical truth or falsity of propositions. It is concerned with formal truth and formal validity. Their learners now after going through these concepts you have to test yourself you have to evaluate yourself that is very small questions to you that is why is Aristotle system of logic formal. And second one is there any difference between symbolic logic and Aristotelian logic I think you have to get the answers in the unit. The second part of this unit that is unit of formal natural, formal logic.