Is psychology a true science?

Pretend that you are in a discussion with friends and the topic is hard sciences versus soft sciences. It is argued that psychology is not a true science at all, as are sciences like chemistry and physics. How would you defend the proposition that psychology is a true science?  What makes a true science? How does a scientist approach defining truth?  Is this how psychologists approach study in their field?

It will be graded by Rubrics

• Include full sentences
• Include at least 3-5 paragraphs (introduction, body [at least one], and conclusion)
• Include reference citations.