You can tell that Mortensen's character is a very radicalized ideologue with perhaps some kind of academic background.  He seems to have some kind of leftist neo-hippie philosophy where the modern world has become corrupted by consumerism, corporations, and perverted science.  He makes numerous mentions to malfeasance of modern institutions like hospitals, the food industry, and the education system.  It is stated later in the movie that his goal was to isolate his family so not only would his children be raised to "philosopher kings" in a unique paradise but also so his wife perhaps would become mentally well.  But it is his own egotism in this regard that pushes his family away from him throughout the movie.