user27550: I'm going through some preparation of the Alapin Sicilian.
Studying the opening I reached this position:
rnbqk2r/pp2bppp/3pp3/3nP3/2BP4/5N2/PP3PPP/RNBQK2R w KQkq - 2 8

In which I wonder why it isn't good for white to take on d5 and give black doubled pawns.
Is because giving the bishop pair in this position is simply too much to just cause doubled pawns to black or are there other reasons? Could you please come up with an example explaining why Bxd5 here is a bad idea?

user4418: 
I wonder why it isn't good for white to take on d5 and give black doubled pawns.

There are a number of problems with this:

First, the doubled (and isolated!) pawns are at best temporary because white has a pawn on e5 which black can take to eliminate the doubled pawns. (Note, by the way, that the suggestion that black can avoid doubled pawns in the first place with the intermezzo Qa5+ and then Qxd5 is wrong. White counters the check with Nc3 protecting the d5 bishop and black has wasted a move forcing white to play a good developing move that was going to be played anyway)
Giving black the opportunity to move the e6 pawn improves black's position because it unblocks the bad c8 bishop which otherwise has restricted mobility.
A much better move is Nc3 which threatens to win a pawn. O-O is also better.

Here is what is likely if white plays Bxd5
[fen "rnbqk2r/pp2bppp/3pp3/3nP3/2BP4/5N2/PP3PPP/RNBQK2R w KQkq - 1 1"]

1. Bxd5 (1. Nc3!) (1. O-O!) exd5 (1...Qa5+? 2. Nc3) 2. Nc3 dxe5 3. dxe5 Be6

The resulting position is probably very even.

27550: <p>I'm going through some preparation of the Alapin Sicilian.
Studying the opening I reached this position:</p>
<pre><code>rnbqk2r/pp2bppp/3pp3/3nP3/2BP4/5N2/PP3PPP/RNBQK2R w KQkq - 2 8
</code></pre>
<p>In which I wonder why it isn't good for white to take on d5 and give black doubled pawns.</p>
<p>Is because giving the bishop pair in this position is simply too much to just cause doubled pawns to black or are there other reasons? Could you please come up with an example explaining why Bxd5 here is a bad idea?</p>
 4418: <blockquote>
<p>I wonder why it isn't good for white to take on d5 and give black doubled pawns.</p>
</blockquote>
<p>There are a number of problems with this:</p>
<ol>
<li>First, the doubled (and isolated!) pawns are at best temporary because white has a pawn on e5 which black can take to eliminate the doubled pawns. (Note, by the way, that the suggestion that black can avoid doubled pawns in the first place with the intermezzo Qa5+ and then Qxd5 is wrong. White counters the check with Nc3 protecting the d5 bishop and black has wasted a move forcing white to play a good developing move that was going to be played anyway)</li>
<li>Giving black the opportunity to move the e6 pawn improves black's position because it unblocks the bad c8 bishop which otherwise has restricted mobility.</li>
<li>A much better move is Nc3 which threatens to win a pawn. O-O is also better.</li>
</ol>
<p>Here is what is likely if white plays Bxd5</p>
<pre><code>[fen &quot;rnbqk2r/pp2bppp/3pp3/3nP3/2BP4/5N2/PP3PPP/RNBQK2R w KQkq - 1 1&quot;]

1. Bxd5 (1. Nc3!) (1. O-O!) exd5 (1...Qa5+? 2. Nc3) 2. Nc3 dxe5 3. dxe5 Be6
</code></pre>
<p>The resulting position is probably very even.</p>
