Theism, from the Greek word theos, meaning god, is a belief in a god, or gods. Theism takes many forms: monotheism is the belief that there is only one God (although monotheists often disagree about just Who that one God is); polytheism, or pantheism, is a belief that there are many gods (which can include monolatry - a belief that one god is supreme over "all the rest"); atheism is the belief that there is no God (although many atheists tend to revere science and popular scientists, who merely study and try to understand God's natural laws).
The Creator Is The Only True God
Honest logic requires that for there to be a creation, there must be a Creator, and that for there to be laws of nature, there must be a natural Law Maker. It's ridiculous to believe that all of the orderly, physical universe could just somehow "happen," without plan and control, from nothing.
That same logic demands that the Creator is the only True God, since absolutely everything else that humans have come to worship (e.g animals, volcanos, the sun, statues, ideas in their own minds etc.) was created by Him - including those who deny His existence, despite the obvious reality that they themselves exist.
Who Is The Creator?
"In the beginning God created the heavens and the earth." (Genesis 1:1 RSV) (see The Seven Days Of Creation)
"Thus the heavens and the earth were finished, and all the host of them. And on the seventh day God finished His work which He had done, and He rested on the seventh day from all His work which He had done. So God blessed the seventh day and hallowed it, because on it God rested from all His work which He had done in creation." (Genesis 2:1-3 RSV) (see God's Holy Day and The Ten Commandments and
The Ten Commandments Now?)
"The Lord is the everlasting God, the Creator of the ends of the earth." (Isaiah 40:28 RSV)
"Father, I desire that they also, whom Thou hast given Me, may be with Me where I am, to behold My glory which Thou hast given Me in Thy love for Me before the foundation of the world." (John 17:24 RSV) (see Jesus Christ
What Isn't God?
"For what can be known about God is plain to them, because God has shown it to them. Ever since the creation of the world His invisible nature, namely, His eternal power and deity, has been clearly perceived in the things that have been made. So they are without excuse; for although they knew God they did not honor Him as God or give thanks to Him, but they became futile in their thinking and their senseless minds were darkened."
"Claiming to be wise, they became fools, and exchanged the glory of the immortal God for images resembling mortal man or birds or animals or reptiles. Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves, because they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator, Who is blessed for ever!" (Romans 1:19-25 RSV)
Fact Finder: What is the Power by which God created all things?