Is Satan real? Can he harm us or cause us to have bad thoughts?

Satan is real. In the premortal life he was known as Lucifer. He rebelled against our Father in Heaven’s plan during the great council in heaven and sought to destroy the agency of man. He was “cast down” and became the devil, the enemy of righteousness and of those who seek to do the will of Heavenly Father. He is the author of deception and lies, a subtle and practiced deceiver. (See Moses 4:1–6.) He and his followers try to imitate the work of God to lead people astray.

Satan uses many techniques to tempt us, but we can triumph over him through faith in the Lord Jesus Christ, obedience in honoring covenants and keeping commandments, repentance, and receiving the proper ordinances. Satan can place temptations in our way and urge us to do bad things, but he has no power over us unless we allow it.

The Prophet Joseph Smith taught, “Satan cannot seduce us by his enticements unless we in our hearts consent and yield. … We can resist the devil; if we were not organized so, we would not be free agents” (Teachings of Presidents of the Church: Joseph Smith [2007], 213).

“When Satan’s lies succeed in deceiving us, we become vulnerable to his power,” said Elder Dallin H. Oaks of the Quorum of the Twelve Apostles (“Be Not Deceived,” Ensign, Nov. 2004, 43).

President James E. Faust said, “I once heard [a temple president] say, ‘The devil is not smart because he is the devil; he is smart because he is old.’ Indeed, the devil is old, and he was not always the devil. … And Nephi states that the devil ‘hath no power over the hearts’ of righteous people. We have heard comedians and others justify or explain their misdeeds by saying, ‘The devil made me do it.’ I do not really think the devil can make us do anything” (“The Forces That Will Save Us,” Ensign, Jan. 2007, 7–8).

At another time, President Faust said, “If we are conscientiously trying to avoid not only evil but the very appearance of evil, we will act for ourselves and not be acted upon.

“Much of what comes from the devil is alluring and enticing. …

“… In simple terms, that which is good comes from God, and that which is evil comes from the devil. You can’t have it both ways and find true happiness; some have tried, but in the long run all have failed” (“The Devil’s Throat,” Ensign, May 2003, 51).

“Protection against the influence of the devil is found by obedience to the commandments and laws of the gospel of Jesus Christ. The message of all the prophets and apostles is that truth, righteousness, and peace shall in the end prevail over error, sin, and war; the faithful shall triumph over all their afflictions and enemies, and shall triumph over the devil. There shall be a complete and lasting victory of righteousness over wickedness on this earth, which will be done by the power of the Lord Jesus Christ” (Bible Dictionary, “Devil”).