One of my favourite topics, and one I will come back to over and over again when contemplating teaching. Are we more a product of our environment or our genes?
There are all sorts of problems with making generalisations on a topic like this, but with a few exceptions I believe nurture is by far the most important factor. I will have to come back to the exceptions later, and explain how very important musical factors such as imagination and portrayal of emotion can be nurtured, but when it comes to pure technical control things are easier to conceptualise. Fundamentally the technical explanations and our understanding of how the body works that have been developed by Flesch, Galamian, Rolland and others show how, with the right knowledge, diligently applied with expert guidance, the limits on what we are able to learn to play are very few.
Most importantly though, how much more enabling is it to believe that our achievements are in our own hands? To believe that those we would like to aspire to are somehow endowed with a gift that we do not have is to be forever limited in our achievements.
Number 1 on my recommended reading list:
http://www.amazon.co.uk/Bounce-Myth-Talent-Power-Practice/dp/0007350546