Since this is going to be a discussion, feel I need to define the word “nominal” as I generally use it when thinking or talking about religion.
“Nominally” can certainly mean “in name only.” The “only” there is important and turns the word into perjorative. But generally when I use the term, especially when I am actually thinking about things, I do not include the “only” on the end and intend the term quite neutrally. I suppose I could say something like “self-described” but that never seems to flow well, and seems somewhat perjorative as well.
What I am really trying to say when I use something like the phrase, “nominal Christian,” is not that I suspect they are not, but rather that I cannot be positive that they are. The problem, as you might suspect, is partly the person under discussion (whether real or theorectical) and partly the definition of what a Christian is.
Starting with the second part, it is somewhat easy to identify the extreme cases. I think that most folks would agree that, say, Saint Francis of Assisi and Mother Theresa were certainly followers of Christ, and therefore Christians, while Madelyn Murry-O’Hare, the famous atheist was not. When you get in between though, things get sticky and vary from group to group. As a Catholic I was occaisionally identified as “not really a Christian” because I did not “accept Jesus as my personal saviour.” On the other hand I have met a couple of Bible thumping fire breathers that seemed so full of anger and hatred that I could not in any way consider them Christian. So, it seems to me that the criteria for “Christian” seems to vary a bit from church to church and person to person, but that does not stop people from identifying themselves as Christian (or not). But of course, God must know who the “Christians” are and are not, but will only sort things out on judgement day, at least according to the common teachings of the church.
Even when a suitable defintion is found, it has to be said that much of what it means to be a Christian is internal. It is clearly not just good works or loving your neighbor, virtually all religious and ethical systems preach that. It also involves some measure of faith and intention for a person to truly be a Christian.
And frankly without knowing a person very, very well it is difficult to gauge the degree to which a person is an actual follower of Christ (whatever that means exactly) and their sincerity in doing so.
So for the purposes of discussion, I often refer to someone as a “nominal” Christian. I mean by that that they have in some way publically declared themselves Christian, either by simply going to church regularly, having been baptised or raised in a faith or by actually proclaiming it themselves. But as we all know, such public actions do not necessarily indicate anything about the person’s inner life and so on.
So for me, other than a few exceptionally well known spiritual figures and a few close friends, every one else is a “nominal” Christian. They certainly look like a Christian, but I have no way of knowing if they walk and quack like one.