The three major issues that cut across psychology are stability versus change, rationality versus irrationality and nature-nurture issue.
Stability versus change deals with the issue of whether human beings change as they grow older or they remain essentially the same.
Rational versus irrationality illustrates the disparity between a human's mind ability to perceive and interpret correctly or incorrectly.
Nature - nurture issue centered on the relative contribution of genetic inheritance and environmental factors to human development.