It depends on circumstances.steph said:I know what you mean~and I think people's opinions on this are very subjective. "Purposely hiding" and "not telling 100%" are too very different things IMHO. I mean, who does that (tell 100%), and who wants someone who does? Not me. Are you happy? Is your partner happy? Then, what of it? Too many people here give way too much info. A simple "I'm going out with friends for a few" ought to suffice in a secure relationship.
XOXO
If "I'm going out with a friend" is understood by BOTH parties to mean "I'm going out window shopping/having lunch/seeing a movie," or something similar, then it's all good. However if the partner staying home understands it to mean that, but the partner going out understands it to mean "I'll be spending a few hours robbing a bank with my buddy," or "I'll be tied to someone else's bed this afternoon," then we have a problem. Sure, that's still "going out with a friend," but clearly there's something there that your partner would want to know about.
It's not important to tell your partner everything. However it IS important to tell your partner everything that he or she would want to know. It's completely possible to deceive someone simply by not telling them the whole truth, or by conveying a false impression through incomplete (but technically true) statements.
Here's a good test: If you're saying "I'm going out with a friend" or some similar shorthand because saying more than that would upset your partner, then you're deceiving your partner.