Every living thing going on progress. Progress is necessary thing for life. In this way development become evidence of life. There is line of demarcation between growth and development. Growth means only physical progress, but development means all kind of progress. It includes physical development, mental development, social development, spiritual development and so on. According to SKINNER development is the continuous and gradual process. HARLOCK of the opinion that development is not limited of growing larger instead, it consists of progressive and series of changes to wards the goal of maturity. Development results in new characteristic and new abilities on the part of individual.

PRINCIPLES OF DEVELOPMENT:

1) PRINCIPLE OF CONTINUOUS DEVELOPMENT:
As per this principle, development is ever going process. SKINNER also agree with this principle, he says that development is continuous and gradual process. The rate of process is some time slow some time fast and some time gets it middle rate. First three years child gets maximum rate of process.

2) PRINCIPLE OF INDIVIDUAL DIFFERENCES:
According to this principle every person has its particular structure of development which makes him different from person to person. We can see differences in two boys or two children of same age. They are different from each other mentally and physically.

3) PRINCIPLE OF HEREDITY AND ENVIRONMENT:
As per principle of heredity and environment, development of child depends on heredity and environment. Development does not depend only on heredity or on environment, but it depends on both environment as well as heredity. Person’s entire personality reflects his heredity and atmosphere in which he grows up.

4) PRINCIPLE OF INTER RELATION:
During the explanation of this principle HARLOCK says that every progress or development depend on each other. Physical development depend on mental development, mental development depend on social development. E.g. when child learn how to walk, mean while he also learn mentally and physically. Thus his physical development depends on mental development and mental development depends on social development.

PHYSICAL DEVELOPMENT:
Physical development means development of every organs of body. From birth to age of 25 children gets its physical development. Our attitude and behaviour depend on physical development. All other development also depends on physical development.

MENTAL DEVELOPMENT:
Mental development is more important then any other development; because person’s social emotion and ethical development depend on mental development. Success of any person depends on mental development. Person’s language, logic, attitude, behaviour etc also depend on mental development. If person is mentally well developed he can face any situation on life.

EMOTION DEVELOPMENT:
Every person has different kinds of passion. He feels pity, fear, jealousy at different time for different person. These passions are depending on emotional development. Balance in all kind of emotion is necessary for better life.

ETHICAL DEVELOPMENT:
Ethical development depends on spiritual and mental development. Devotion, love, forgiveness etc come under ethical development. For ethical development prayer, social welfare and spirituality is become necessary. Above mention all kind of development depends on different stages of life. A child can not immediately develop spiritual development. He suffers from different stages of life and among these stages he develops different stages of development. Thus entire development of men depend on different stages of life, WILLIAM SHAKESPEARE introduce seven stages of life.