-A Reader Asks: Sullivan, in An Introduction to Philosophy (available thru ITOPL), also says that common sense and philosophy are connected. It seems that the two would go against each other because common sense is something that general people know and philosophy is a way of looking at things from a technical or scientific perspective.
-Ite ad Thomam answers: Well, I guess I would say that philosophy and common sense are both similar and different. They are similar insofar as the perennial (traditional) philosophy of Aristotle and Aquinas proceeds from natural human reason and experience, which is what people normally call "common sense." But philosophy transcends or goes beyond common sense insofar as it analyzes it and reasons through it, making sense of it all.
Let me illustrate. In his philosophy, Aquinas gives proofs of the existence of God. But his proofs are not convoluted, abstract argument (like those of other before him, for example, Anselm--we'll talk about him). Rather, his proofs all begin from a simple observation of the world around him. For example, one of his proofs, the fifth, starts from the observation that the universe around us has an intricate order and design. In other words, it is not chaotic, but rather, everything in nature has a specific function and orderly purpose. Plants, for instance, take in the carbon dioxide that we breathe out and process it to make their own food; in turn, the byproduct of this process comes out: oxigen, which we in turn breathe. And the whole universe is replete with such intricate order and design, from the molecular level to the gallactic level.
But given this fact from common sense, Aquinas goes beyond it. From it he concludes that there must be an intelligent designer responsible for ordering creation in such a brilliant manner. So he brings in his logic and realizes that:
Premise 1: The universe is a design.
Premise 2: Every design has a designer.
Conclusion: Therefore, the universe has a Designer.
So, in summary, Aquinas begins with common sense, but since common sense by itself is not sufficient to reach a precise understanding of reality, he needs to transcend common sense and bring in analysis and logical reasoning, so as to attain a more scientific understanding of the world around us. This is, in essence, Fr. Reginald Garrigou-Lagrange's main point in his book, Le sens commun: La philosophie de l’être et les formules dogmatiques, which is, without a doubt, the best work ever written on this issue. Unfortunately, it hasn't been translated into English yet. If you can read French, I truly recommend it. (If you can't read French, this book alone is a good reason to start learning French!) You can obtain a PDF version of this book through ITOPL.