you and blackstone are both looking at the word from a personal point of view whilst I was looking at it from society's.
Initially, when I thought about this, it seemed to make all the difference in the world, but actually I'm not so sure. Both definitions are ultimately legalistic, in the sense that aren't you are assuming, whether in a court of law or one's own conscience, that, if it causes arousal, it's bad? Doesnt this still lead to the notion that any sexual arousal is then somehow bad - in an orthodox, dualistic way? Whilst it is perhaps easier to think in this black, white way, I dont see that it has anything much to do with human life as I see it happening from day to day. Nor do I see that it has much to do with the gospel. Bearing in mind the parable of the Tax-collector and the Pharisee in the temple, let's say that we are immensely strong-willed and stay away from sexual arousal for days and days on end, we are then tempted to be pleased about this as though this level of purity somehow raises us a couple of notches closer to God.
This is relevant to me at the minute because I have been ill for some time now and my illness renders me pretty well libido-less. It means that sex has become utterly irrelevant to me, and I have been constantly tempted to think that this has somehow helped with my spiritual life. But I know that the spiritual life doesnt work like this: 'the purer I am the closer I am to God'. It's a dangerous blind alley, and parable after parable in Jesus' teaching shows me I am heading for a fall the longer I travel up it.
I am quite certain that God does not count purity or sexual abstinence of any significance whatever (although it may seem so to us): which isnt to say that it isnt therefore relevant: its just that its not the criteria by which He judges, and is therefore not the criteria by which we should judge our own lives.
So when I say that it is legalistic to think like this, bear in mind that society will always judge legalistically because it cannot see into the heart. We however are called to live not by 'right or wrong' but by the law of love which, whilst being linked, is still quite, quite different.
I know I have raised the stakes here, but it still seems important to bear in mind the dangers of discussing morality per se.