I'm reading Daniel Dennett's excellent new book Intuition Pumps And Other Tools for Thinking, and so I am taking this opportunity to present an Intuition Pump that I use that has helped me enormously when it comes to trying to understand questions of ontology - about what is real. This Pump is to consider the significance of someone actually saying the words which describe their belief about reality. Words are a result of movement of mouth and lungs and throat, and that movement is under control of our brains. This is utterly uncontroversial and yet has great significance, because it means that for someone to speak justified words in support of the reality of a thing, that thing has to somehow make that person's brain act differently, no matter how indirectly. Again, this seems trivially true, but just consider the significance of this when it comes to subjects such as the nature of consciousness and matters supposedly supernatural. For conversation to be meaningful someone has to say what they believe is real because what they believe is really is real, and the cause of someone saying a thing involves brain function. This utterly destroys the idea that there is any sensible concept of non-interacting dualism, because no speech about that idea can be because of the truth of the idea.
Try this Pump on other ideas - I have found it to be extremely effective!