God never asks us to believe, without giving sufficient evidence upon which to base our faith. His existence, His character, the truthfulness of His Word, are all established by testimony that appeals to our reason; and this testimony is abundant. Yet God has never removed the possibility of doubt. Our faith must rest upon evidence, not demonstration. Those who wish to doubt will have opportunity; while those who really desire to know the truth, will find plenty of evidence on which to rest their faith.—Steps to Christ, 105.
The Bible unfolds truth with a simplicity and a perfect adaptation to the needs and longings of the human heart, that has astonished and charmed the most highly cultivated minds, while it enables the humble and uncultured to discern the way of salvation. And yet these simply stated truths lay hold upon subjects so elevated, so far-reaching, so infinitely beyond the power of human comprehension, that we can accept them only because God has declared them. Thus the plan of redemption is laid open to us, so that every soul may see the steps he is to take in repentance toward God, and faith toward our Lord Jesus Christ, in order to be saved in God’s appointed way; yet beneath these truths, so easily understood, lie mysteries that are the hiding of His glory,—mysteries that overpower the mind in its research, yet inspire the sincere seeker for truth with reverence and faith. The more he searches the Bible, the deeper is his conviction that it is the Word of the living God, and human reason bows before the majesty of divine revelation.—Ibid., 107. WGD 9
The personality of the Father and the Son, also the unity that exists between Them, are presented in the seventeenth chapter of John, in the prayer of Christ for His disciples: “Neither pray I for these alone, but for them also which shall believe on Me through their word; that they all may be one; as Thou, Father, art in Me, and I in Thee, that they also may be one in Us: that the world may believe that Thou hast sent Me.” John 17:20, 21. MH 421
And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life. 1 John 5:20, KJV