This is known as the fallacy of
petitio principii (begging the question / circular logic).
There are two meanings of this expression - the original version and how the expression has come to be used by many: «Begging the question» derives from the
Latin petitio principii - «a request for the beginning or premise».
«It's a translation of the Latin
phrase petitio principii, and it's used to mean that someone has made a conclusion based on a premise that lacks support,» writes Grammar Girl, who explains the complicated subject well in her blog.
Thus begging the question, is related to the circular argument (circulus in probando, «circle in proving»), although Aristotle, who was the first to
define petitio principii treats them as separate concepts.
When asking the question about the validity of the science, they assert the science is
valid petitio principii.
For example, to believe that a book is true because the author of the book says it is, would be an example
of petitio principii or begging the question, because the premise on which you are basing your conclusion has not been proven.
This argument involves
a petitio principii.
However, even if Hartshorne did seriously want to hold that view he would be committing
a petitio: God exists necessarily if at least some concretum exists necessarily, and some concretum exists necessarily because God's power insures it.
This begging aspect, or
petitio, is what is known in formal rhetoric and debate as the sin of «begging the question.»
One such major sin goes by the not so obscure Latin name of a «
petitio.»