The many factors which divide us are actually much more superficial than those we share. Despite all of the things that differentiate us - race, language, religion, gender, wealth and so on - we are all equal concerning our fundamental humanity.
Material objects give rise to physical happiness, while spiritual development gives rise to mental happiness. Since we experience both physical and mental happiness, we need both material and spiritual development. This is why, for our own good and that of society we need to balance material progress with inner development.