Nope, lust would be, as he said, “thought of fornication.” This delight he’s mentioning is whatever pleasure might come from a kiss, even without impure thoughts.
Erm. I would disagree with St Thomas there. There is more probability that he is right than that I am. He’s a saint, he was a genius, he was a priest. This said, he was still prone to human errors and he was not a bishop teaching in communion with the Pope. He was not infallible.
He should also not be taken out of context. If you can kiss your mother on the hand or your daughter on the forehead, you can do each to a woman who is your fiancee or girlfriend or dear friend. You do not do this without some form of delight.
Personally, I think St Thomas was more right than we are ready to accept, but I don’t think that he was completely right.
To what Joseph L. Varga said (I’m trying to avoid quotations to make posts shorter), the default kiss on the mouth between young people who “are in love” makes them forget the meaning of other kisses or other gesture such as hugging. This culture is all about clingy slow-dancing and going full-on with the kissing, but that is basically like giving stronger impulses to those who are desensitised.
Once in the youth group we discussed this with our parish priest, and he also said that kissing was sinful. So I think this is actual teaching of the Church, not just St. Thomas Aquinas’ opinion (yes he made that mistake with the 40 days; he also doubted the Immaculate Conception but said he would submit to the Church’s teaching if the Church was going to take a position on the issue). But, passionate kissing is not the same as kissing, say, your parents on the cheek. The “holy kiss” representing brotherly love is still a part of liturgy in Eastern Orthodox Churches (probably in Eastern Catholic Churches, too).
People kiss their relatives and that’s not sinful (and neither did St Thomas say it was), as you say. The holy kiss would derive from that, not from anything romantic. I have a lot of doubts on the romantic kissing, but I would not label it as uniformly and inevitably sinful. The touching and kissing with delight may be some form of trying to get ahead of time and treat the other person like a spouse when he or she clearly is not. This is similar to objections people raise against cohabitation in so far as sex is not included in it.
I believe there’s nothing in the Magisterium to warrant such far-reaching conclusions or at least make them obligatory. My highschool priest said kissing was fine if it was meant to show affection but it was not fine when it was meant to satisfy lust.
I think the problem with passionate kissing is that in retrospect, it often has served to do something else than we thought when we were doing it. This is because we want to do it, so we are looking for excuses and we are unwilling to see it as wrong. All in all, say, we’re marrying someone finally. Don’t we wish we hadn’t at least not French-kissed or kissed passionately with others before?
I would warn against seeing kissing as “our thing”, “something to do”, “a little indulgence” and so on. It might not be actually wrong, but it draws parallels to the sexual intercourse which is missing from that relationship and may be construed as a replacement. And our abstinence from premarital sex isn’t to be built on replacements.