What is an argument?

"Succinctly, an argument is a discourse intended to persuade. You persuade someone by engaging their doubts and providing evidence to overcome those doubts. A journal article, then, is a piece of writing that attempts to persuade a reader to believe in something. It expresses a point of view intended to influence.
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More technically, an argument is a coherent series of statements in which the author leads the reader from certain premises to a particular conclusion. Thus, an argument always has at least two parts: a claim and evidence for that claim. A statement that is being supported is called the conclusion, hypothesis, or claim. A statement being offered as a support to another is called a premise, proof, or evidence. Whatever your argument (or thesis or conclusion) you must provide proof (or premises).
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I use the term "argument" as shorthand for your article's significant idea, an idea you must support with proofs to persuade the reader that your point of view has validity.
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An argument is a dialectic between opposing positions that results in a decision. It is about the search for answers through exchange. This means that you do not need to have an unassailable argument, just an interesting one. A difficult truth is that those issues most worth arguing over almost never have all the evidence on one side or the other: Both sides have compelling proofs... To persuade readers, they must first have doubts, or believe that others have doubts that your argument is right. So, to construct a sound argument, build in a consideration of opposing voices. This is a mark of the best academic writers.
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It's a good writer's job to show that opposing arguments are understood and credited, but need not vitiate the claim. Good reasons exist on both sides of any important argument; your purpose is to present them and reach the best conclusion possible.
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In the social sciences, such openness often shows in the authors' description of the limitations of the study. The authors analyze their data as supporting their hypotheses, but admit that variations in sample or variables might have delivered a different conclusion.
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an argument is about establishing a position through rational support." (Belcher, 2009, pp. 82-90)

Belcher, W. L. (2009) Writing your journal article in 12 weeks: A guide to academic publishing success. Thousand Oaks, CA: SAGE Publications, Inc.