Lex Orandi, Lex Credendi. The idea that your worship affects your beliefs (and vice versa). There's certainly some truth there.
I would like to suggest a new Latin-esque soundbyte:
Lex Hang-around-y, Lex Credendi
Call it peer pressure, call it influence, whatever. I have noticed that who you hang around with also tends to affect your theology. For good... or for ill.
1) This has been true for me.
a. Who I "hang" with: As I have been a pastor for 6 years now, those pastors around me have had an effect on my perspective. Not that I have essentially changed what I believe (I am still a Lutheran, I still hold to my ordination vows, the confessions, etc...). But I do think differently about theology, the LCMS, and being a pastor.
b. What I read: Reading from many sources, but especially making use of the treasure of good Lutheran theology available on the internet, I have also shaped my views over the years. In fact, I probably read more now than I did in seminary.
2) This is true for many laypeople I have observed.
a. Those whose family and friends are made up of Baptists, Evangelicals and the like, tend to be less Lutheran in their thinking. Those laypeople who attend inter-denominational Bible studies (like BSF) seem to have a "fuzzier" Lutheran self-identity.
b. I sometimes take note of what people read. There are many Lutherans who study Rick Warren, Max Lucado, Billy Graham, and watch the TV preachers. This has to rub off on you eventually, especially when you are not reading these ideas "critically". I remember my little-old-lady shut-in who said, "Pastor, the Baptist minister on TV stands there and preaches RIGHT FROM THE BIBLE! Isn't that wonderful???"
So maybe this whole post is just an exercise in noting the obvious. But it's worth reminding ourselves, I think, that people's theology can be, and IS influenced by association.
I think this has implications for our understanding of church fellowship.
I think it impacts our choice of school/college for our children.
I think this has implications for what VBS program we choose.
I would also want to consider the very prevalent idea in the LCMS that we can just take what some non-Lutheran has done or written and "Lutheranize" it.
I mentioned this in my post about CCM. It occurs to me that many on the "less traditional" side of the LCMS take this approach to other things too.
Take Rick Warren. I seem to remember the Lutheran Witness ran two perspectives of his book. One (the main article) said there were some problems but that we could basically Lutheranize Warren, and pluck the pearls of wisdom from among the false teachings.
The other perspective (the sidebar), by Professor Pless, was less kind to Warren. If memory serves me, he compared Warren's work to a car in which the engine was missing (or something like that). In other words, that when the Law drives the theology, the whole thing is "broken".
(I also read this analogy somewhere too: "Saying that Warren's PDL is basically good but with some problems is like saying, 'gee Mr. Lincoln, wasn't that a nice play though?")