As a young man, Witmer wanted a better future and a better world after the social problems he saw as a result of the Civil War.

In 1884, Witmer enrolled at the University of Pennsylvania to study art, but after a couple of years he transferred to the Finance and Economy department where he obtained a Bachelor's degree in 1888, aged 20.

After a stint as a teacher, Witmer decided to return to the University of Pennsylvania for his graduate studies in political science.

While he was teaching at the academy, Witmer noticed that a 14-year-old student who wished to go to college had extreme difficulties in differentiating sounds, as well as other speech problems that might today be called dyslexia.

Witmer decided to help him to correct his problem; the child progressed satisfactorily and was able to continue studying, eventually enrolling at the University of Pennsylvania.

The following year, Witmer decided to attend graduate school at the University of Pennsylvania and was accepted into the Philosophy department.

Witmer and Cattell worked together to found an experimental psychology lab with the purpose of studying individual differences by examining a range of subjects.

He also began conducting research on individual differences in sensory-perceptual variables and presented papers in experimental psychology.

During March of that year, a special case was brought before him: a 14-year-old student was having extreme difficulties learning to spell, yet was quite able and excelled in other subjects.

[5] In 1908, he established and staffed a small private residential school near Wallingford, Pennsylvania, an institution dedicated to the care and treatment of retarded and troubled children.

Witmer and other experimental colleagues proposed that the APA should accept only psychological papers, be separated from the American Philosophical Association, and have a better selection process for choosing new members.

Witmer told Titchener that the association should be only for men and that women should be excluded because they were too emotional when discussing scientific issues.

[7] He eventually changed his attitude, and decided to teach female students; accepted women to work at his clinic, and later appointed a woman to manage it.

[8] Witmer opened the first Psychological Clinic at the University of Pennsylvania in 1896, with the purpose of studying children who had either learning or behavior problems.

Witmer's main participants were children who attended public schools from Philadelphia and surrounding areas, and who were brought to the clinic by their teachers or parents.

In the clinic, Witmer regularly dealt with issues such as speech difficulties, sleep disturbances, behavioral problems, hyperactivity and refusal to stay in school.

In its first issue, he published the article "Clinical Psychology", which explained its definition in the following way: Although clinical psychology is clearly related to medicine, it is quite as closely related to sociology and pedagogy... An abundance of material for scientific study fails to be utilized, because the interest of psychologists is elsewhere engaged, and those in constant touch with the actual phenomena do not possess the training necessary to make the experience and observation of scientific value...I have borrowed the word "clinical" from medicine because it is the term I can find to indicate the character of the method which I deem necessary for this work.

In his article, Witmer presented the idea that all kinds of children (smart or mentally retarded) could reach their full potential with help.

[citation needed] Witmer studied monkeys and a chimpanzee trained for theatre performance called Peter.

He found Peter could string beads, light and smoke cigarettes, unlock padocks with keys hammer nails, turn on taps, and write the letter "W" with chalk on a blackboard.

[citation needed] In 1911 Witmer supported a bill in the state of Pennsylvania to sterilize severely retarded people, with the purpose of minimizing their offspring.

[citation needed] In his 1896 APA paper, cited to be the first instance of his use and explanation of the term "Clinical Psychology," Witmer outlined four main goals for his new discipline.

Witmer's fourth goal was to train more psychologists to become experts in working with mentally and/or morally intellectually disabled clients.

According to Witmer, for clinical psychology to actually be of any worth, it needed to help and improve clients' mental health and well-being.

Witmer highlighted the concept of treating each client as an individual, and not simply as a physical manifestation of their problem or a phenomenon to be observed and explained.

He emphasized examining each client's personal background history, as he believes it would allow clinicians to better and more fully understand their situation.

[12] Witmer was the first psychologist to undertake and focus, on the treatment of those with mental, physical or moral handicaps with the goal of improving their deficits.

By mixing normal and handicapped children, Witmer gave these professionals the chance to directly observe the differences between the two groups for themselves.

By 1930, the University of Pennsylvania presented him with a volume called Clinical Psychology: Studies in Honor of Lightner Witmer.