Everything we perceive takes place in time and space, and every change has a cause. But according to Kant, that is not because of the way reality ultimately is: it is a contribution of our minds. We don't have direct access to the way the world is. Nor can we ever take the glasses off and see things as they truly are. We're stuck with this filter and without it we would be completely unable to experience anything. All we can do is recognize that it is there and understand how it affects and colours what we experience.