What was going through William Shatner’s head when he recorded his cover version of ‘Lucy in the sky

My five best guesses would be
1) "Space" dust
2) The thoughts of a lost love affair
3) The active agents in cannabis, smack or LSD
4) Career angst
5) The firm belief that he was a pioneer

Merry christmas Mr Shatner and Merry Christmas Wibsite Folks!