Word for having a definite opinion while simultaneously withholding judgment?

Someone with this attitude would have a definite or even strong opinion on a given issue, but would also be willing to change their mind should new information arrive. The word could also be used to describe someone who was open minded, but also had a clear working opinion which they were prepared to use with confidence.

An example of this would be an Agnostic who nevertheless considers it very unlikely that God exists. But the meaning shouldn't be limited to a religious context.

Agnostic is close, but only seems to describe the open minded aspect of the attitude, not the having a definite working opinion aspect.

Any ideas?

Perhaps scientific

conforming with the principles or methods used in science: a scientific approach

The scientific method is defined as

principles and procedures for the systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses

Scientists (and others practicing the scientific method, in work or their everyday lives) routinely have viewpoints, opinions and hypotheses about issues, but are ready to modify those positions based upon new evidence.

And, in anticipation of any objection that the initial example given was in the religious context, numerous scientists believe that their scientific approach is not incompatible with their religious beliefs, and many argue that their scientific approach demonstrates the validity of their religious positions.

Albert Einstein provides an example of the view that science and religion are compatible.