[[this is mostly gonna be copy-paste ala bulbapedia]]
"It's not that bad, look!" Grey said, holding it up.
The book was open to the first page in the chapter on basic philosophy:
In a broad sense, Pokémon training is based on the answer to two questions: What should the relationship between a Pokémon Trainer and Pokémon be, and what is the best way to foster this relationship? Depending on their individual viewpoints regarding training, different Trainers follow different methods of training and focus on different areas. It is generally thought that there is no one right way to train, since many methods have valid reasons behind them and their own set of advantages and disadvantages.
However, in particular, many training methods will fall into one of two categories. The first category is methods which focus on the happiness and well-being of Pokémon and developing a bond of friendship. The second category is methods which focus on developing the strength and ability of a Pokémon and being able to control it masterfully. Trainers will often argue about which of these two views is best. In fact, this is a common theme in the canon, frequently supporting the idea that friendship is the most important thing in a Trainer's relationship with Pokémon, and a good Trainer can bring out the strength of any Pokémon with their love and care.