Early in one's practice on The Path to Enlightenment there will be a pollution in the mind known as Doubt. This includes, doubt about:
Doubt is not eliminated through blind faith or by convincing oneself that The Teachings are true. It is instead through seeing enough progress made in one's own mind after Learning, Reflecting (to independently verify) and Practicing The Teachings (with guidance from a Teacher) that doubt is eliminated.
( see section "How to Determine If A Potential Teacher Has Attained Enlightenment" from Chapter 3 of The Words of The Buddha book series for guidance about selecting a Teacher )
There can be doubt in the historical existence of Gotama Buddha and doubt about whether or not he achieved Enlightenment. This can be further complicated by not understanding what Enlightenment is.
Here is a Mini-lesson about Enlightenment:
It is through seeing The Natural Laws of Existence taught by Gotama Buddha in the world that a Practitioner can know with certainty that Gotama Buddha existed.
Achieving higher levels of peace, calmness, joy and Enlightenment then enables a Practitioner to know for themselves that Gotama Buddha (the source of these Teachings) was Enlightened.
Doubt about The Teachings involves not knowing or understanding if The Teachings are true. It also includes doubt about whether or not The Teachings lead to your Enlightenment.
Doubt is not eliminated through belief, but through seeing results for oneself, such as anger decreasing over time. Eventually, anger and all other discontent feelings (ie. sadness, frustration, irritation, annoyance, guilt, stress, etc.) will never arise again.
( see The Words of The Buddha book series for a complete set of Teachings with guidance from a Teacher – Free of Cost. )
Doubt about The Community includes doubting whether or not The Community of students practicing The Path to Enlightenment are practicing the straight way, the upright way, the wholesome way and the way leading to Enlightenment.
Doubt about your Teacher includes not knowing or understanding if your Teacher can guide you towards Enlightenment. It can also include doubt about whether or not your Teacher is Enlightened.
Sometimes a student can project their own conceit, sensual desire, ego and ill-will onto their Teacher, making it difficult to know if a Teacher is Enlightened.
( In the Introduction of this post a resource was shared for determining the ability of a Teacher to guide you towards Enlightenment. )
It's beneficial to study with a Teacher who is Enlightened or close to Enlightenment. If you study with a Teacher who is not in the 3rd or 4th Stage of Enlightenment they may recommend another Teacher.
There can be confidence in The Buddha, The Community, your Teacher and confidence that The Teachings lead to Enlightenment but doubt about whether or not you will be able to do what is required to attain Enlightenment.
By the time a student achieves The First Stage of Enlightenment (as a Stream Enterer) they will have completely eliminated all doubt. This is done through dedication and consistent effort.
If you have questions, you can consult with Teacher David – Free of Cost.
@chrisriceChris Rice joined the Hive community in 2018 with a strong interest in helping and contributing to its growth. Some of his contributions include co-founding Hive Philippines and starting the 
He lives in Davao City, Philippines with his wife and son, where he dedicates much of his time to studying The Teachings of Gotama Buddha with guidance from Teacher David Roylance.
One of Chris’s life goals is to provide objective evidence that many modern-day “mental illnesses” can be resolved through training the mind.
