1. Logic cannot deduce the existence of elementary facts. Elementary facts are facts that can only be known through observation alone.
2. Valid logic does not always lead to correct conclusion. Logic can deduce the conclusion by finding the relations between elementary facts. But the elementary facts have to be available first (see no. 1 above). If you start with wrong elementary facts, you will get wrong conclusion, eventhough you have a valid reasoning.
3. The correct conclusion will still be limited by the elementary facts being given. If new elementary facts are given, the conclusion might change.