If the person is influenced by ideas that oppose what he believes in..

If the person is influenced by ideas that oppose what he believes in on a matter pertaining to one of his convictions:

Either his faith is not settled although he professes that he believes in that thing, that is to say his faith is not complete and firmly grounded.

Or he might be making assumptions based on the contents of his mind which is not accurate, and thus he falls into doubt under the influence of his impressions.

These two states are caused by:

The person’s insufficient grasp of ilm (knowledge in the Islamic context),

His inability to pass through imitation and get to scrutiny,

His inability to rid himself of assumptions and doubts,

His inability to become sincere in surrender and submission,

His inability to discern whether the inspiration he received is from an angel or the devil, his ignorance about stations regarding the explanation of the matter at hand and his subsequent inability to correctly perceive the wisdom, and his inability to have grasped the truth that judgments vary according to stations.

Allah (ﷻ) knows best.

Ahmet Şahin UÇAR