The Shahada is the gnosis of God and all his messenger(s). It is to accept the one and only Almighty Creator and his last messenger Mohammed (peace upon him). The concept of one God is called Tawheed.
Importance of shahada it is enough to say that you have reached the side of safety. When someone says that ‘I am a Muslim’ it means he or she accepted and admitted Kalimat at-Tawheed, Kalimat ash-Shahada, "ashhadu an la ilaha illa Allah wa ashhadu anna Muhammadan Rasulullah".
To become a Muslim means accept the shahada, or else you are not a Muslim. By saying "I am a Muslim" you have passed the first level. Then you have to go to the second level. It means you have said, "O Allah I admit that you are the Creator and I am your slave." Slave, not servant.
In the law, testimony is a form of evidence that is obtained from a witness who makes a solemn statement or declaration of fact. Testimony may be oral or written, and it is usually made by oath or affirmation under penalty of perjury. Unless a witness is testifying as an expert witness, testimony in the form of opinions or inferences is generally limited to those opinions or inferences that are rationally based on the perceptions of the witness and are helpful to a clear understanding of the witness' testimony.
Schools of Thought in PsychologyFrom structuralism to cognitivism, numerous schools of thought have emerged throughout psychology's history. Many of these theoretical outlooks have dominated the field at certain points in history. Learn more about some of the major schools of thought in psychology in the following articles and resources.