Common sense. What is it? What is meant by it? Is it real? Common sense is just that: a common impression men have from their experience, an impression acquired through our senses (all knowledge is ordinarily acquired through our senses). The world is constantly impressing things on us through our senses, and from this we acquire our concept of reality. It is frequently simple common sense that finally and at lasts rejects a philosophical error that is approaching its mad conclusion ("everything is fake! there is nothing real in reality! everything is meaningless"), as it begins to contrast itself - even violently - with everything that we know and daily experience.
Truth powerfully impresses itself upon us exactly because we have no power to prevent it from doing so. It would require a nearly superhuman effort to avoid absorbing the impression(s) reality makes upon us. From this we have, as it were, a base or foundation of certainty that we can draw from and apply, compare, contrast, etc.; and we do this without even consciously thinking about it. That is why the Apostle speaks of certain of God's attributes being known through the things that He has made. Those things make impressions upon us.
Every single human being - certainly by the age of reason, at least - already has an encyclopedia worth of sense impressions, such that he can already generally predict and expect the ordinary occurences of daily life. He can anticipate not only natural phenomenon but even people's behaviour and reactions toward him depending on his own actions, etc.
Exactly, therefore, because both truth and reality are objective, and because they impress their truth and reality upon us, we can speak of and deal with things objectively; that is, based on what we know about them, with certainty. I know, for example, that I am not a couch. I also know that I am not an irrational animal. I know that I am a man. I know that when there is an absence of light, there is darkness. Based on these seemingly innocuous truths, there is already latent or potent within them a great many and other, perhaps more important truths.