Just want to share a very precise statement of the beliefs that I currently find very hard to oppose. It's actually from the catholic encyclopedia website.

I. Materialistic Naturalism

Materialistic Naturalism asserts that matter is the only reality, and that all the laws of the universe are reducible to mechanical laws. What theory may be held concerning the essence of matter makes little difference here. Whether matter be considered as continuous or as composed of atoms distant from one another, as being exclusively extension or as also endowed with an internal principle of activity, or even as being only an aggregate of centres of energy without any real extension (see ATOMISM; DYNAMISM; MECHANISM), the attitude of Naturalism is the same. It claims that all realities in the world, including the processes of consciousness from the lowest to the highest, are but manifestations of what we call matter, and obey the same necessary laws. While some may limit their materialistic account to nature itself, and admit the existence of a Creator of the world, or at least leave this question open, the general tendency of Materialism is towards Atheism and exclusive Naturalism. Early Greek philosophers endeavoured to reduce nature to unity by pointing to a primordial element out of which all things were composed. Their views were, implicitly at least, Animistic or Hylozoistic rather than Materialistic, and the vague formative function attributed to the Nous, or rational principle, by Anaxagoras was but an exception to the prevailing naturalism. Pure mechanism was developed by the Atomists (Democritus, Epicurus, Lucretius), and the soul itself was held to be composed of special, more subtile, atoms. In the Christian era materialism in its exclusive form is represented especially by the French school of the latter half of the eighteenth century and the German school of the latter half of the nineteenth century. Since matter is the only reality, whatever takes place in the world is the result of material causes and must be explained by physical antecedents without any teleology. Life is but a complex problem of physics and chemistry; consciousness is a property of matter; rational thought is reduced to sensation, and will to instinct. The mind is a powerless accompaniment or epiphenomenon of certain forms or groupings of matter, and, were it suppressed altogether, the whole world would still proceed in exactly the same way. Man is a conscious automaton whose whole activity, mental as well as physiological, is determined by material antecedents. What we call the human person is but a transitory phase in the special arrangement of material elements giving rise to special mental results; and it goes without saying that in such a system there is no room for freedom, responsibility, or personal immortality.

I do want to add here that I believe that this system can and does allow freedom and resposibility. In fact, this is primarily what my thesis will be arguing for. I'm not sure about personal immortality though.