What is the Meaning of “What is the meaning of Life?”?

If the question “What is the purpose of life?” is fundamental and important, surely it begs two questions.

i) Why assume that there's a purpose of life (or a purpose to life) at all?

ii) Why should there only be one purpose (one meaning) to life?

Usually, when people ask this question it's because they think they believe that they already know the answer. Such people are really asking the following question:

“Do you want to know what the purpose [meaning] of life is?”

And the answer will usually be a religious one; though sometimes it may be “spiritual” or have something to do with what the questioner himself thinks the purpose/meaning of life is.

People may have their own views as to what the purposes of their own lives may be for themselves. Though what they believe doesn't depend on their also believing that there's a single purpose to/of life which they must somehow discover. (Or that they need to be told what it is by someone else.)

That still wouldn't be the purpose/meaning of life. It would be a purpose of life for a single individual. What one person sees as his purpose to/in life isn't the purpose of life. It's the main purpose of his life. Nothing more.

Basically, when most people ask “What is the purpose/meaning of life?” they believe that this purpose/meaning exists separately from human minds.

Of course such a belief can become more metaphysical or complex than the way I've expressed it.

For example, physically it can be said: 

There must be a primary thing from which everything else owes its existence. 

However, where does purpose or meaning fit into that belief? We could all owe our physical existence to the First Cause or to the Big Bang. However, there's no built-in purpose or meaning here unless it's argued for; rather than simply assumed. (Most biological things owe their existence to air and water – are they “primary things”? Is the purpose/meaning of life air and water?)