The second quote mentions the number four; wedrifid was referring to that, not the number four.

Aha! I didn't even read the other quotes and just went straight to quote number four.

I don't think that suggesting new definitions for words is problematic if it helps. In the case of calling a tail a leg it would deprive the word leg of most of its meaning. But the case of calling two charities departments of a single charity highlights a problem with Steven Landsburg's advice for charitable giving:

So why is charity different? Here's the reason: An investment in Microsoft can make a serious dent in the problem of adding some high-tech stocks to your portfolio; now it's time to move on to other investment goals. Two hours on the golf course makes a serious dent in the problem of getting some exercise; maybe it's time to see what else in life is worthy of attention. But no matter how much you give to CARE, you will never make a serious dent in the problem of starving children. The problem is just too big; behind every starving child is another equally deserving child.

This disregards the fact that problems like cancer, heart disease or hunger consist of a huge amount of sub-problems, many of which need to be tackled at the same time to make the main objective technically feasible.

What if you were able to assign weight to the various problems that need to be solved in order to reach the charity's overall goal? You would do so if you didn't believe that the charity itself was efficiently distributing its money among its various sub-goals.

Take for example the case of the Singularity Institute. If people could weight various of the SI's projects by defining how their money should be used, some people wouldn't support the idea of rationality camps.

And here it is useful to view the SI and FHI as two departments of the same charity. They both pursue goals that either support each other or that need to be solved at the same time.

If you were to follow Landsburgs argumentation, if you were interested in defeating hunger, you might just contribute to a project that researches certain genetic modification of useful plants. Or why not contribute to the company that tries to engineer better DNA sequencers?

My point is that the concept of a charity is an artificially created black box with the label "No User Serviceable Parts Inside" and Landsburg's argument makes it sound like we should draw a line at that point and don't try to give even more efficiently. I don't see that, I am saying that in certain cases you can as well view one charity as many and two charities as one.