To be expert in critical thinking is to be able to take one’s thinking apart methodically, to examine each part, evaluate it for characteristics and afterward, advance it. The first step in this method is understanding the elements of thinking, or fundamentals of reasoning. These elements include reason, assumption, viewpoint, concepts, and propositions. An assumption is something we presuppose or take as fact. Typically, it is something we learned earlier and do not doubt. In other words, it is part of our classification of values. Human beings unpretentiously and frequently use our beliefs as assumptions and make conclusions found on those assumptions. We have to do so to create a good judgment of where we are, what we desire, and what is occurring. Assumptions infuse our lives specifically as far as we cannot proceed without them. We drive conclusions, form explanations, and come to conclusions built on the viewpoints we have produced.

The structure of logical argument can be summarized by the following: fundamental unit of what may be supported or denied is the proposition (or statement) that is classicaly articulated by a declarative sentence. The principal concern of logic is how the truth of certain propositions is associated with the truth of an alternative. Therefore, most often we treflect on a group of related proposals. An argument is a set of two or more propositions linked to each other in such a way that all except for one (‘the premises’) are expected to supply support for the one that is left – ‘the conclusion’. The transition or movement from premises to conclusion, the logical correlation between them, is the deduction upon which the argument is built.
Fallacies can be divided into two common groups: ‘formal’ and ‘informal’. A formal fallacy is a flaw which can be identified simply be looking at the logical construction of an argument rather than any precise statements. Informal fallacies are defects which can be recognized only through an examination of the actual subject matter of the argument.
A “valid” argument is one in which if the premises were all true, then the supposition would have to be true as well, as far as it comes out from the accuracy of the premises. Nevertheless, a line of reasoning can be “valid” but enclose untrue premises. A sound argument is the one that is valid, but in addition has all ‘true’ premises. Soundness requires both validity and the condition when all the premises are true. For soundness, you really are concerned about the truth of the premises in the actual world, not some made up one that you may reflect on when considering about validity.