So that we may understand this question well and correctly, let us remember what Jesus said in the Gospel of John:
If you love me, keep my commandments. And I will entreat the Father, and he will give you another Comforter, that he may abide with you for ever. The Spirit of truth, which the world cannot receive, because it neither sees nor knows it; but ye know him, because he dwelleth with you, and shall be in you. [...] but that Comforter, the Holy Spirit, whom the Father will send in my name, he will teach you all things, and remind you of all that I have spoken unto you. 
From the words of Jesus, it appears that the mission of the Promised Comforter is to guide men to the Truth, re-establishing the teaching of Christ in its primitive purity and opening new horizons to human understanding of life.
During the history of mankind there were, according to the teaching given by the superior spirits, three revelations: The Decalogue, which constitutes the divine part of the Mosaic law; the moral teaching contained in the Gospel and Spiritism. The first revelation of God's law is personified in Moses, the second in Christ, and the third is not personified in any person, the first two being individual and the third collective being the essential character of Spiritist revelation.
Spiritism raises the veil cast over some mysteries, brings enormous consolation to the disinherited of the earth and to all who suffer, giving a just cause and a useful goal to all human pains. Christian revelation has succeeded Mosaic revelation and Spiritist revelation completes it. Christ has announced it, and he himself presides over this new outbreak of human thought, manifesting itself outside and above the Churches, his teaching is directed to all races, because it is based on love and not religious dogma, that is, Spirits everywhere proclaim the principles on which it is based, inviting man to meditate on God and the life to come.
The third revelation, unlike the others, is not personified in one individual because it arose simultaneously in thousands of different points, is collective in the sense that it is not made or given as a privilege to any person, being distributed simultaneously over the earth, confirming Joel's prediction: “In the last times, saith the Lord, I will pour out my spirit upon all flesh; your sons and daughters shall prophesy, the young men shall see visions, and the old dreams. ”
Spiritism does not teach anything contrary to Christ, but develops, completes and explains, in clear and objective terms, what has not been said except in allegorical form. He comes to fulfill, in the times predicted, what Christ has announced and to prepare the fulfillment of things to come. Spiritism does not dogmatize or immobilize. Without any pretense to infallibility, its teaching is progressive as the spirits themselves.
To grasp the true meaning of the words spoken by Jesus, it was necessary that new ideas and new knowledge brought the indispensable key. However, these ideas could not arise before the spirit of humanity had acquired a certain degree of maturity, it was essential that science could contribute powerfully to the outbreak and development of such ideas. Therefore, it was necessary to give science time to grow and progress.
By reading the words of Jesus in the Gospel of John, we find that the Promised Comforter should have some special characteristics, namely: Try to remember what Jesus taught; Teach many things that the Gospel could not adequately explain; To comfort and comfort those who suffer by showing the cause and purpose of human suffering, and the Comforter, as the Spirit of Truth, would then have to give man knowledge of his origin, the necessity of his sojourn on earth and his destiny, spreading the consolation that comes from faith and hope everywhere.
There was a need for further referral from the Promised Comforter because not all was said by Jesus, because of the immaturity of humanity at the time, the forgetfulness, lack of experience of truths preached in the Gospel and the premeditated distortions that the gospel message suffered throughout the years. times for the church (Christianity). As Kardec addresses in The Genesis were two thousand years of fermentation and criminal deformation of the Christian message.
And when asked if Spiritism can fulfill all the conditions inherent to the Comforter, the answer is surely positive. Such reasoning is very clear in the Gospel According to Spiritism , when Kardec states that Jesus promises another comforter, saying that the world did not yet know the Spirit of Truth because he was not ripe to understand it, but that the Father would send another comforter to teach all things and to remember what Christ had said. He points out that if the Spirit of Truth had to come later to teach all things, it is that the Christ had not said everything, and if he comes to remember what the Christ said, it is a sign that the above was forgotten or misunderstood.
Notes also that Spiritism has come to open the eyes and ears of all, speaking precisely without figures or allegories, intentionally lifting the veil over certain mysteries, allowing the supreme consolation to reach the disinherited of the Earth and to all who suffer, thus fulfilling all the conditions cited by Jesus in his promise. Therefore, just as Christ said “I did not come to destroy the law, but to fulfill it”, so Spiritism says “I do not come to destroy the Christian law, but to execute it”, not abosolutely teaching anything contrary to what he taught. Christ, but only by developing, completing and explaining it in clearer terms and for everyone.
João 14:15-17 e 26.
Atos 2: 16-18.
KARDEC, Allan. O Evangelho Segundo o Espiritismo.131 ed.Brasília: FEB, 2013. p. 105.