Most of our reality is created by our thinking. Consider, for instance, the lines on a road. These boundaries, which tell us that different regions of the road are appropriate for different purposes, are artificial boundaries created by our thinking but which have real power and substance as a result of our obedience of this convention.
Consider also money. Money has value only by convention, but as a result of this convention it is a very real thing with which it is possible to get a lot done and exercise a lot of power. The power of money is a reality, but it is a reality created by our thinking.
Similar comments apply to language, legal codes, art, possessions, social roles and social status, social norms, etc. It is not only true that some of our reality is created by our thinking; indeed, it might appear that the majority of our reality is created by our thinking. Most of the external world is like the lines on the road.
This was pointed out by the social constructivists. The social constructivists generally go further in the following way. As has just been pointed out, there is a category of things that are socially constructed and which we know to be socially constructed. There is also probably a category of things that are socially constructed and which we do not know to be socially constructed, but think to be constructed by some force outside humanity.
The position of the social constructivists is, in essence, that this latter category is large, and that we frequently make the mistake of ascribing to forces outside humanity things that are really due to forces within humanity. Without taking this position we can nonetheless acknowledge that most of the daily reality that we navigate is, in a very uncontroversial sense, socially constructed.