It could be that the person you want to date is simply at the stage of their life where they're just not interested in settling down or being part of a couple. Perhaps they've just come out of a long-term relationship and need some time to heal and move on, maybe they're concentrating on other aspects of their life right now, such as their career, and do not have the time or energy to commit to someone, or it could be that they're just happy with their own company and living the single life.
If this is the case, and they are completely honest and upfront with you about this from the start, then you may feel that it may still be worth seeing this person on a more casual basis. This type of 'relationship' can work out well, as it allows both parties to enjoy each others friendship as well as share a physical closeness.
However, this advice comes with a serious proviso. Don't even contemplate casually dating someone who has quite clearly told you that they do not want a relationship unless you are not looking for anything more serious either. It's a fatal mistake to get involved, hoping that they'll change their mind one day.
The important thing is to listen to, respect and accept their need to be unattached, whilst also accepting and respecting what you need. Be absolutely honest with yourself here, it will save you a great deal of frustration and heartache in the future. If you feel that you do want more, either with them, or with someone else, then move on and find someone who CAN offer you what you're looking for.
