Here is an interesting reference from Bertrand Russell to support the above thesis.
Russell believes the task of philosophy [critical thinking, etc.] explore the No-Man's-Land while anchored on the definite knowledge of Science and other faculty of knowledge.Bertrand Russell wrote:THE conceptions of life and the world which we call "philosophical" are a product of two factors: one, inherited religious and ethical conceptions; the other, the sort of investigation which may be called "scientific," using this word in its broadest sense. Individual philosophers have differed widely in regard to the proportions in which these two factors entered into their systems, but it is the presence of both, in some degree, that characterizes philosophy.
"Philosophy" is a word which has been used in many ways, some wider, some narrower. I propose to use it in a very wide sense, which I will now try to explain.
Philosophy, as I shall understand the word, is something intermediate between theology and science. Like theology, it consists of speculations on matters as to which definite knowledge has, so far, been unascertainable; but like science, it appeals to human reason rather than to authority, whether that of tradition or that of revelation.
All definite knowledge--so I should contend-belongs to science;
all dogma as to what surpasses definite knowledge belongs to theology.
But between theology and science there is a No Man's Land, exposed to attack from both sides; this No Man's Land is philosophy.
Almost all the questions of most interest to speculative minds are such as science cannot answer, and the confident answers of theologians no longer seem so convincing as they did in former centuries.
Science tells us what we can know, but what we can know is little, and if we forget how much we cannot know we become insensitive to many things of very great importance.
Theology, on the other hand, induces a dogmatic belief that we have knowledge where in fact we have ignorance, and by doing so generates a kind of impertinent insolence towards the universe.
Uncertainty, in the presence of vivid hopes and fears, is painful, but must be endured if we wish to live without the support of comforting fairy tales.
It is not good either to forget the questions that philosophy asks, or to persuade ourselves that we have found indubitable answers to them.
To teach how to live without certainty, and yet without being paralyzed by hesitation, is perhaps the chief thing that philosophy, in our age, can still do for those who study it.
Introduction - The History of Western Philosophy
Theists relying on theology - unanchored on definite knowledge - take the big leap across
the No-Man's-Land to the LA LA LAND of the certainty of a dogmatic belief that they have knowledge where in fact they have ignorance.
This is why theists are never able to prove the existence of God as real or even possible because there is no tracks to trace back to any grounds of definite knowledge.