I was taught as a teenager the Worldview of C.S. Lewis, for which I am grateful, as there are many worse starting points. I think my view of faith and reason as well as the neo-Platonism of Lewis that we learned in philosophy allowed me to fit well into the Catholic faith. Unlike the nominalists (anti-rationalists) Luther and Calvin, Lewis fell more closely to the Angelic Doctor (Aquinas), through Lewis' study of Dante, and in his clever use of reason, I understood how Christianity shouldn't be afraid of philosophy.
But I did learn many unhelpful views that I'm only now philosophically unpacking. Our epistemology (method of finding truth) was Berkeleian Immaterialism. It was basically this argument:
Ideas are true or false
Matter/Material Objects is/are not true or false
Therefore ideas are not Matter/Material
This gave us "spirit" which wasn't material, or 'idealism' at least. Then we would go on to attack Empiricism with the typical Cartesian methods, as well as Berkeley's which sought to show how the senses were unreliable. Ex:
How do you know you have proper vision?
you hear the doctor say you passed a vision test
How do you know you have proper hearing? , etc to infinity where one can no longer believe anything based on the sense, but by the mind alone / reason.
This is the argument Bishop (Anglican/CofE) Berkeley used to argue for immaterialism, the idea that the only 'real' existent things are ideas perceived in one's mind. This then led to the problem of: 'what happens when someone isn't thinking about an object? does it cease to exist?' - we know the things don't cease to exist, as we do not when we sleep, etc. This means a universal mind must be perceiving everything at once (a Term Lewis uses in Mere Christianity for God - he was a Berkeleian after all). This universal mind is God.
Thus cometh the famous phrase that "we are all just thoughts in the mind of God".
This was a fun worldview because it was diametrically opposed to materialism, the worldview of the modern university. Then I remember reading Nietzsche's "Twilight of the Idols" and his chapter on how the real world became myth, etc. It wasn't so much of a logical argument that disarmed me / immaterialism, it was just an interesting approach which many people would prefer to my pseudo-platonic arguments.
Like I said, Nietzsche never really convinced me logically of anything (that's kind of his whole point really), but it did much to shake my thinking. Subsequently I've read Christians who attack his post-modernism from a Modernist Christian standpoint, and I've seen other Catholics and Protestants accept postmodernity and understand Catholicism within it (Kearney, Vattimo, MacIntyre also kind of).
I then started studying Aquinas, and I began to love his way of doing things. He mixed the 'best' of neo-platonism with aristotelianism, and made it all Christian. But there was one problem... He was an empiricist (the view, you'll remember, of my oldest enemies). He described the intellect and soul ascending to God from perceiving sensible things. But when I read "Nicomachean Ethics" by Aristotle last year and his "Politics", I felt like I "gave my mind to Aristotle" (like I gave my heart to Christ), because he was such a genius. But I'm still trying to figure out Aristotelianism and my own life.
The advantage I do see in St. Thomas - aside from his legacy and centrality in our Holy Roman Church - is the way his system seems so true in everyday life. It is a challenge though to my normal Platonic system which has a heavy emphasis on distinguishing between mind and body, matter and spirit. This has been a key theme in my life (probably why I'm obsessed with learning and education, but morbidly obese, or why I am great with faith, but terrible with works). Aristotle, and St. Thomas always make sure that the internal and the external are linked, and that grace perfects nature. That sounds really simplistic but in reality it's REALLY profound. In my previous worldview matter was almost evil, corrupted by the fall, grace abolished nature, it didn't perfect it. The material world was the fake and transient world, the world of the forms or ideas was the 'real world'. Aquinas will have none of this. God is reconciling even nature to himself, and evil is only a privation of good, Christ gave us physical things - sacraments (baptism, eucharist, etc) - to change our spiritual reality by grace. This means faith and works, nature and grace, the natural and supernatural, are all married to some extent. For instance he writes on the Law of Christ:
"The kingdom of God consists chiefly in internal acts: but as a consequence all things that are essential to internal acts belong also to the kingdom of God. Thus if the kingdom of God is internal righteousness, peace, and spiritual joy, all external acts that are incompatible with righteousness, peace, and spiritual joy, are in opposition to the kingdom of God; and consequently should be forbidden in the Gospel of the kingdom." - St. Thomas Aquinas (http://www.newadvent.org/summa/2108.htm)
I didn't go to church/mass today, even though I could've, because "I didn't feel like it", and because I couldn't receive the sacrament anyway (I'm as usual, in mortal sin). I figured regardless of whether or not I sat in church today, my relationship with God would be uneffected. But Aristotle reminds us that virtues are formed by habitual action and repetition. St. Thomas and Catholicism likewise oblige us to attend Mass regularly because this physical habit changes our spiritual reality, it makes God's Word more prevalent in our mind, it makes our Will more easily inclined towards the work of God, and it brings us into deeper fellowship and even allows us to spiritually partake in the oblation (Sacrifice of the Mass) of the priest/Christ.
But in my own choice of will, I demoted my intellect to my passion of laziness, and thus missed another chance at grace. This is how philosophy changes my life, and our lives. Perhaps you should look over your own philosophy, after all, according to Socrates: "the unexamined life is not worth living".