Learning to read and write makes little sense if you don't understand what you're reading and writing about. While we may have forgotten, most of our early learning came not from being explicitly taught but from experiencing. Kids aren't born knowing hard and soft, sweet and sour, red and green. When the child experiences those things, s/he transforms them into psychological understandings. When kids play with other kids, they learn about others and about themselves. Learning the basics of our physical and social reality is what early childhood is all about.