Final causes

I'm interested in understanding more about final causes, after reading Edward Feser's blog post, The Return of Final Causality, and the paper it links to, Does Efficient Causation Presuppose Final Causation.

What is a final cause? From what I understand, Aristotle said that every change requires four things (four "causes"):

• efficient (the doer of the change)
• material (what the changing thing is made of)
• formal (the nature of the changing thing, common to all things of that type)
• final (the normal result of doing what the doer is doing)

For some reason, most contemporary philosophers reject #3 and #4. I'm not sure why.

The basic idea of a final cause is given by the last sentence of the paper:

It is not empty to assert that all efficient causes are aimed at something.

Sometimes when you do something, the result is different than normal. Regarding this, the paper quotes Aquinas:

...in inanimate beings, the contingency of causes arises from imperfection and deficiency: because by their nature they are determined to one effect, which they always produce, unless there be an impediment due either to weakness of power, or some extrinsic agency, or indisposition of matter. For this reason natural causes are not indifferent to one or other result, but more often produce their effect in the same way, and seldom fail.

 I am going to re-read Feser's book The Last Superstition. Some questions I will have in mind while reading it are:

1. I would like to understand Aristotle's ideas better (act and potency, form and matter, the four causes.)
2. What reasons have we to believe that these ideas are true?
3. Which of Aristotle's ideas do moderns reject and why?
4. What problems does the rejection of these ideas cause?