If I am going to start learning design, I am going to ask this question first - "What is design?" But the search for the answer leads directly into philosophical statements and arguments. I am lost then. What I am trying to say is, while searching for the answer in real world, how could I know I have developed that required aesthetic sense of observation. After that how can I implement my learning and experience in designing real world products.
Why do leftists have a broad set of ideals and people on the right also a set of different ideals? Why, generally, do women like romance novels (words) in the same way that men like colorful magazines (pictures)?
There are a lot of answers to those questions directly [try Google], but the philosophical point is knowing the context. If you want to write a book with mass appeal about science, you need to leave out the equations. [Forward to "A Brief History of Time"], but that's just marketing.
What you want is to develop is a feeling for a balance of form, function and target audience, or, as Barnett Newmann put it:
"Aesthetics is for the artist as Ornithology is for the birds."