Talk:Irelia/@comment-4710042-20120523021817/@comment-4957501-20120523052724

You're not supposed to build it if you have plenty of farm solo top. Plenty of farm means you're doing very well. You get a Philo Stone on Irelia if you're having a tough time sustaining in lane against your opponent due to constant harass/ganks, leading you to being zoned heavily and as a direct result losing farm. Rushing your core anyway in such a situation is a bad idea, since the constituent items of your core won't affect your sustainability by much and you'll still have to constantly recall or risk being killed, losing heavy farm and xp in the process. In this case, it would be much more beneficial to buy a Philo Stone. The HP regen gives you a huge boost to your sustainability, the mana regen allows you to Q that creep you might've missed otherwise more often and the Gp10 helps make up for lost farm. It even pays for itself after about 13 minutes, and you can keep it around for longer to give your income a small boost. The only downside of this is like you said, it delays your core. But it doesn't delay it by much in the end, and in most cases it would actually help you get your core faster due to not having to recall as much and as a result losing that farm. Don't buy it if you don't need to though.

Philosopher's usually isn't worth it on AP Mid's and is very situational, however Kage's is a pretty solid item since most AP items have few constituent parts, so you won't miss the item slot much until the end of mid/late game rolls around and it'll pay for itself twice over by that time if you get it early. It also builds into MET and DFG, so if you're going for those, definitely worth it to get it early. As an AD carry though, building Gp10 items is a pretty big no-no.