basically, should I consider that what-sentence is in apposition with that-sentence?
Many sayings contain germs of truth, and some are indeed profound, but they aren't reliable sources of knowledge and can be misleading. For example, take the saying 'You can't teach an old dog new tricks'. This isn't true of all dogs, and certainly isn't true of all human beings: there are many older people who are capable of making radical leaps in their ability. This is not to deny the effects of ageing. The point is that what is roughly true, that as we get older it becomes harder to learn new behaviour, is not true for everyone in every respect.

1)what does "germs of truth" mean?
2) in the second line from below, there is the 'that-led' sentence rightly following the sentence "what is roughly true,"
basically, should I consider that what-sentence is in apposition with that-sentence?

Please help me!
Thanks!!

Question

basically, should I consider that what-sentence is in apposition with that-sentence?
Many sayings contain germs of truth, and some are indeed profound, but they aren't reliable sources of knowledge and can be misleading. For example, take the saying 'You can't teach an old dog new tricks'. This isn't true of all dogs, and certainly isn't true of all human beings: there are many older people who are capable of making radical leaps in their ability. This is not to deny the effects of ageing. The point is that what is roughly true, that as we get older it becomes harder to learn new behaviour, is not true for everyone in every respect.

1)what does "germs of truth" mean?
2) in the second line from below, there is the 'that-led' sentence rightly following the sentence "what is roughly true," 
basically, should I consider that what-sentence is in apposition with that-sentence?

Please help me!
Thanks!!

Answer

Germs of truth in this case means a very small measure of truth. Germs are tiny, so if something has a "germ" of something, it's going to be really, really small.

The other sentence is pretty complicated, but if you take it apart it will make more sense. If you take out the clause that is separated by commas -- "that as we get older it becomes harder to learn new behaviour" -- you are left with "The point is that [what is roughly true], is not true for everyone in every respect.

"What is roughly true" is treated here as a single thought. The phrase separated by commas is an explanation or example of "what is roughly true".

More simply stated, the sentence means: "It is roughly (somewhat) true that as we get older it becomes harder to learn new behavior. However, this is not true for everyone in every respect. That is the point."

I hope that's helpful!

Answer

germ means:

An initial stage from which something may develop;

Example:  the germ of a brilliant idea.

I don't think anyone actually knows what "germs of truth" means, though many people believe they themselves do.

What does it really mean when someone says "it is an initial stage from which truth may develop.  I don't think one develops truth.  The verb for truth is "discover".  One discovers truth.  There is a book called "Germs of Truth".  It does not mean, however, that the term is good English or that anyone understands it.  There is a lot of bad English in the world.

The passage you quoted is one good example.  I would not bother with it if I were you.