First, when Greek Platonic Idealism (sometimes called realism) replaced the non-Platonic parts of the gospel. (Somewhere around the third century AD).
Second, when Aristotelian Nominalism (the competing Philosophy) came in and replaced Idealism for some. (Somewhere around the twelfth century).
Third, any popular philosophy they encounter in the Church that they don't agree with.
For an example:
- Idealism: beauty is a property constructed in the mind, so exists only in descriptions of things.
- Platonic realism: beauty is a property that exists in an ideal form independently of any mind or description.
- Aristotlean realism: beauty is a property that only exists when beautiful things exist.
- Anyone who is famous has beauty (neo-calvinism/popular culture).
Platonic thought is found every time someone reads scripture and assumes that any particular concept refers only to a specific ideal form, that can be discovered without regard to the context of the person doing the discovery. Thus the discussions about faith (which is used in several different ways) where every use of it is treated as fungible and the same as any other.
Aristotelian thought is found every time someone says there is no meaning outside of context. Even better, modern, popular versions of Aristotelian thought are not the same as the "real" thing (as a philosopher would see it).
You can think of the one as black and white thinking and one as endless shades of gray.
The relevance is that there are two movements in the Church. One is to strip everything of context -- to the point that while John Taylor may have used the word "Priesthood" in multiple different ways (as a replacement for the term "brotherhood" and other times as an inherent quality and other times as "authority") any time he uses the term is treated as being properly switched for any other time as if his uses were fungible. I doubt that Plato would identify with this descendant of his thinking.
The other movement is to reduce everything to context, combined with the assumption that modern popular context is superior. Thus anything that opposes the popular culture is evil and meaning becomes very fluid, depending on the needs of popular culture. This leads to the words of Christ being used to justify violent aggressive war, free love and sex without responsibility, and the idea that we are now beyond sin. Aristotle would not recognize this as his thought.
But both of these trends pull us away from Christ. When asked to choose between the Pharisees and the Sadducees, Christ did not embrace one over the other. He was neither, in the popular parlance, a Liahona or a Iron Rodder. Instead he gave commandment to go beyond those dividing lines, to embrace charity and devotion, and to take upon us the name of Christ.
I think we learn something when we choose to do that rather than mingle philosophy with scripture.