This is a fairly common occurrence. The person you meet who has been in about 5 different denominations tells you that all those denominations worship the same God. The implication (stated or unstated) is that we should stop fighting anything, since we all worship the same God. To them, no other doctrines seem to matter except the doctrine of God. Now, there is a grain of truth to this plea. We should never ignore common ground that we have with people from other denominations, as that is usually a good place to start, and shows good will. However, the unity that is usually (and rightly!) desired by people who believe in the same God cannot be achieved by simply stifling debates and lowering other doctrinal matters to the status of insignificance. This unity cannot happen by simple fiat. It is in fact naive to think this way. In fact, the emphasis really ought to be in focusing on our differences, so that the Biblical record can be examined once again to see if these things be so. A book I read fairly recently by a Roman Catholic author quite convincingly argues that ecumenical endeavors that focus entirely on common ground will inevitably stall. Instead, our attention should rather focus on the areas of disagreement. People these days seem to be allergic to disagreement. Folks, disagreement does not equal hatred!
It is not true that the doctrine of God is the only doctrine of importance. It is quite obviously of central importance. However, we cannot reduce Christianity to our doctrine of God. What about our doctrines of Scripture, Christ, man, salvation, Holy Spirit, church, and sacraments? Are they now to be completely ignored in the interests of ecumenicity? Honestly, many of the early heretics of the church would have claimed to worship the same God we do. And some of them would have been correct. Just because one is correct in one’s doctrine of God (posit, for instance, that a person is orthodox in his doctrine of the Trinity) does not mean that one is orthodox in all other areas. One could have a correct view of God, but a heretical view of Christ’s natures, for instance.
Lastly, it is not always true that these denominations have the same view of God as the other denominations. We have said before that it is not enough to state the truth in a positive way. The wrong views must also be refuted and denied. Many mainline denominations may have correct statements about the doctrine of God. However, functionally speaking, they will not discipline a minister who holds to a heretical view of God. If a denomination states an orthodox view of God, but then does not discipline their ministers for heretical views of God, then that denomination is not holding to an orthodox view of God. The reasoning for this is simple: the denomination, by failing to discipline heretical views, is stating that a variety of views on God’s person is acceptable. That is their functional position. People have forgotten just how important the denial of errors is (especially in today’s theological climate!). Of course, this also underlines the importance of church discipline for the church. I would argue against those who exclude discipline from the definition of the true church. Without discipline, the church stands for nothing. Without discipline, the church is like parents who never spank their children: they are abusing their children! It is, in effect, not parenting at all.
We really need to think much more carefully about this ecumenical business. It does need to be done. However, we need to be wise in how we do it. We can never shove differences under the rug. Otherwise, a superficial unity will result that pleases no one, least of all God, who wants a church unity that is characterized by the truth.