One of the things about Modern Orthodoxy that often gets overlooked is the meaning of the word "modern".
It seems to usually mean that MO's dress in modern clothes, have modern interests, appreciate modern secular knowledge, and so on. Unfortunately it also gets implied that the "modern" doesn't so much influence the "orthodox" as the other way around.
But the problem with the word "modern" is the same problem with the word "now". Neither really indicates much. If "now" is this instant in time, well by the time I've finished typing that the "now" that was is in my past, much further back by the time you read this.
It's the same with "modern". Folks back in First and Second Temple times didn't call themselves "ancient". That term was reserved for the original Egyptians and Hittites, possibly also our ancestors who came out of Egypt. And as much as we like to call ourselves a modern society nowadays, folks in the 23rd century will be talkin about us as living on "old Earth". Watch Star Trek if you don't believe me.
If this is the case, then the "modern" in "Modern Orthodox" cannot refer to simply being trendy with whatever is hip in secular society while maintaining an Orthodox approach to life. Rather, it should refer to the way Judaism interacts with the surrounding culture and how it takes from it elements of use to one's practice.
It seems that there's an intrinsic tension in the word "modern" since what it defines is always changing but in another respect it's always the same since it's the latest and greatest. How does one bring that concept into our practice of Judaism?
Years ago a Conservative rabbi (I think it might have been Elliot Dorf but don't quote me) compared the halachic decision making process to a game of chess. After the Torah was given and the Oral law develop the pieces moved into different positions as new situations came up. The Orthodox approach nowadays, he contended, was to place a glass dome over the board so the pieces could no longer move. The Conservatives, on the other hand, were still moving the pieces and allowing halacha to evolve.
He never mentioned the Reform but I could suggest that their approach was to clean all the pieces off and use the board as a coaster for their drinks.
I don't think this analogy is very accurate, though. For one thing, there is clearly continued motion of the pieces on the Orthodox chessboard. It's just that the Chareidi approach to moving the pieces is to create new rules that limit options, like allowing the queen to either go straight or diagonal but not both, or restricting the rooks to a maximum move of 4 spaces at a time. For them, the mesorah is defined as unchanging but this is clearly not correct if one looks at how normative Orthodox practice has evolved over the centuries.
For another, it could quite easily be proven that while the Conservatives are still moving the pieces but that they've tossed the rule book into the garbage. For them, queens (and this is not a backhanded reference to their recent legitimization of homosexual marriage) can move in any direction and jump like horses while pawns can move backwards and rooks can jump over bishops. The pieces and board are the same but the game being played is unrecognizable to someone familiar with the rules. For them, change is the whole point and the guiding light is secular society.
Where does that leave Modern Orthodoxy? Well, to persist with the chess analogy, both the Chareidi and the non-Orthodox approach leave an excellent option to be used: playing with the actual rules. The rules of chess which guide the motion of the pieces are unchanging. They are the "Modern" in Modern Orthodoxy.
What this means is developing a model of Orthodoxy based both on traditional halachic principles and academic scholarship to obtain a deeper and more accurate understanding of the mesorah. It means saying to the non-Orthodox that what they are playing is not chess, no matter how much they want to think it is and that they therefore cannot legitimately claim to be halachic and taken seriously. And it means saying to the Chareidim that their limitations on the rules, their adjusting of how the halacha is developed is also in violation of the rules.
Full halachic practice requires knowledge and confidence. It requires knowledge is that a person needs to know the sources he is dealing with, from the Torah through the Talmud down past all the Poskim. It requires confidence in that difficult situations or a lack of ready facts cause people to say "assur " just to be careful. This is not halachic practice. It is a cop-out.
Therefore it must be proposed that Modern Orthodoxy develop this model: a traditional model of halacha including the traditional rules for adjusting it to changing circumstances while maintaining absolute fealty to the mesorah.