"Look unto me in every thought; doubt not, fear not." (D&C 6:36)
To doubt is to be in a "state of uncertainty with regard to the
truth or reality of anything; undecidedness of belief or opinion." To
doubt is to waver, to be uncertain, to be hesitant. There is also a
sense of the word doubt that implies to dread or to fear or to be
afraid of something. To doubt also is defined as "uncertainty as to the
truth of Christianity or some other religious belief or doctrine"
(Oxford English Dictionary).
The Indo-European root for the word doubt comes from the word two.
So "if you are in doubt you are of two minds" (The Origins of English
Words).
There are a number of Greek words which are translated into the word
doubt in the New Testament. Essentially, they have very similar senses.
For example, one of the senses of the word doubt means to "stand in two
ways." Another sense means "to be without a way" (Vines Expository
Dictionary of New Testament Words). In the New Testament context, the
word doubt sometimes means to be perplexed or to not know the way
forward.
Often we think of doubt and unbelief as synonymous. Of course, there
are many similarities between doubt and unbelief. However, doubt
implies more of a sense of being paralyzed, unable to move forward; not
seeing a way forward. In this sense, it is easier to see the connection
between doubt and fear. Also, in this connection it is interesting to
reflect on the verse, "A double minded man is unstable in all his ways"
(James 1:7).
On the other hand, the stripling warriors were fearless in battle
because "they had been taught by their mothers that if they did not
doubt, God would deliver them" (Alma 56:47).
While doubt and unbelief may often be synonymous, it is clear that
in all cases doubt is the opposite of faith. Moroni teaches that we
need to believe "in Christ, doubting nothing." And that in our prayers
we must "doubt not, but be believing ... and come unto the Lord with all
your heart" (Mormon 9:21, 27).
President Gordon B. Hinckley taught, "As each man or woman walks the
way of life there come dark seasons of doubt, of discouragement, of
disillusionment. In such circumstances, a few see ahead by the light of
faith, but many stumble along in the darkness and even become lost. My
call to you, this morning, is a call to faith" (Ensign, May 2002).
Famously, President Thomas S. Monson has taught, "Remember, faith
and doubt cannot exist in the mind at the same time, for one will
dispel the other. Cast out doubt. Cultivate faith. Strive always to
retain that childlike faith which can move mountains and bring heaven
closer to heart and home" (Ensign, May 2005).