From this point of view faith may be rational or blind. 

Blind faith does not exam anything and accepts the good and bad without any checking and at every step it comes to conflicts with the obvious truth and rational mind. Its extreme form is f a n a t i s m. 

It is the faith that is based on faults; sooner or later it will suffer a shipwreck as only those are insured in connection with the future which does not have any fear from the spreading of brightness because what is true in darkness is true in brightness as well.

Every religion thinks that solely they own the real truth. Those who claim blind faith in connection with each point of their faith they confess that they are unable to prove their truth. (1)

It is said that faith is not a force, many people say it is not their fault they do not have faith. 

It is undoubted that faith not a force but it is more true that faith does not force itself to anybody. It is not a force but it is obtainable and there is really no one, not even the most stubborn, who would deny they do not have any faith. We are talking about fundamental spiritual truths not about particular faith. It is not the faith’s task to find people but the people’s to find faith, which they will find if they act sincerely. Those who say ‘We do not wish anything else more just to believe but we are not able to do it (2)’ they only say it with their mouth but not with their heart because while they say this they shut their ears. As the evidences pullulate around them, so why are they reluctant to see them? It is called negligence for some people while to others it is a fear from changing their habits and for most of them it is haughtiness that does not wish to know a higher power to bow in front of. 

There are some people who seem to born with faith and a moment is enough for it to develop. This sensibility is a sign of an older development towards spiritual truths. 

While for others it emerges hard which is a clear sign of backwardness in development, the previously mentioned ones could believe earlier and knew and with their reincarnation they brought the intuition of what they had already known. Their raising had been finished while the latter mentioned ones have to learn everything. Their raising is coming now which is going to happen too. If it does not happen in this life then it happens in another one. 

The resistance of an unbeliever sometimes does not come from their fault rather from that method the things are represented for them. 

Faith needs base; this base is the perfect understanding which faith needs. For believing, it is not enough to see but above all to understand. Blind faith is not good in our century since the tenets of blind faith provide the most part of the unbelievers by forcing itself to people. With this, it deprives the two most precious privileges like the freedom of thinking and the free discernment. Blind faith is mainly this. Unbelievers protest against it and it can be said with rights that faith is not a force by not providing any evidences but leaves uncertainty in the spirit which gives birth to doubting. 

However sensible faith that leans on facts and logic does not have any dimness. 

We believe because we feel certain, and a man only can be certain if they understand and they do not let it. Because only that faith is immovable which stands with rational mind face to face in any era of the humanity. Spiritism leads to this result which wins triumph over and over unbelief only if it does not meet regular interest-originated resistance. 

1 – The newer spiritual revelations make differences between the ’faith’ in God and Christ’s leading and the ’religion’ with dogmas. (the editors)

2 – Our spiritual leaders say that faith is the graceful present of God which people have to develop with endless work. (the editors)

Extract of Allan Kardec: Gospel in reflection of Spiritism