This is my second of five posts in a series on the Argument from Consciousness. The Argument from Consciousness, you may recall, begins by presenting properties of consciousness which cannot in principle be explained on a naturalistic ontology.  It then argues that it is credibly probable that agents with these mental properties will exist if there is a God but incredibly improbable that they would exist if there is not. In other words, the existence of conscious agents with mental properties that cannot in principle be reduced to the physical implicates the existence of a Nonphysical Conscious Agent as their originating cause. My first post in this series discussed qualia. In this post I will be discussing a property of mental states which philosophers of mind call, “intentionality.”
A second property of mental states that defies naturalistic explanation is what philosophers call the “intentionality” or “aboutness” of thought. By this they simply mean that all thoughts have the property of being about or of something external to themselves. When you think about shoes and ships and sealing-wax, for example, your thoughts are in those moments of or about shoes and ships and sealing-wax—a property, moreover, that is inescapable since even the thought, “Thoughts do not have intentionality,” if it is to be meaningful, must itself be about intentionality and therefore have intentionality. The denial of intentionality would therefore suffer from what Plantinga calls, “self-referential inconsistency,” and cannot be rationally affirmed.
The intractable problem intentionality raises for naturalism can be drawn out in the following way. Consider the word moon penciled on a piece of paper. In the absence of a literate observer to read the word and associate it with the moon, can the carbon particles of pencil lead and the wood pulp that composes the sheet of paper be said to be “about” the moon? Clearly not. And what can be said of a penciled word on the page can be said equally of physical brain states. A pattern of firing neurones representing someone’s thought about the moon cannot, in the absence of a conscious observer to experience that brain event as a thought about the moon, be said to be “neurones about the moon” in any meaningful and objective sense. Physical things (whether they be neurones or particles of pencil lead or teapots or rocks) are not “about” other physical things in the way that mental states undeniably are. And so an exhaustive naturalistic description of mental states would leave something essential to them out of account.
This is the second property of consciousness that is insusceptible of reduction to the physical
 To affirm a “naturalistic ontology” is to affirm the metaphysical position that everything arises from natural properties and causes and so that supernatural or spiritual explanations are to be excluded or discounted. On a naturalistic ontology mindless particles organised in various ways by mindless forces is all that exists.