My guess from the context is that he lacked the filling of the Holy Spirit because it says that he only knew of John's baptism. It seems odd that he wouldn't have the Spirit. He clearly believed in Jesus since Acts 18 says that he preached the story of Jesus accurately. Other parts of scripture imply that we receive the Spirit when we believe. So this is why there is confusion.
But if you read between the lines of the early faith stories the "normal process" (not that it was a formula) to coming to faith was that someone believed, was baptized in Jesus name and filled with the Spirit all at once. People didn't wait to be baptized as they do today. It was immediate. And that seemed to be the time when the Spirit came to indwell the new believer...similar to how the Spirit came in the form of a dove upon Jesus at his baptism.
Jesus brings a little clarity to the issue in the book of John, chapter three. He talks to Nicodemus about the difference between being born of water (baptism) and the Spirit. A religious act isn't good enough. We need the genuine presence of God. He said...
All that to say that we need to be careful not to assume we have the Spirit of God in us just because we have a casual belief in Jesus...we grew up in church...went through confirmation...have read the entire Bible...been baptized, etc. A relationship with God is more than knowing information about God or performing a certain rite of passage. It involves his Spirit living inside of us, directing us and transforming us. I'm sure many people have walked away from God because their knowledge alone didn't change them and it left them frustrated. This was Nicodemus' problem in John 3."Very truly I tell you, no one can see the kingdom of God without being born again. "4 "How can anyone be born when they are old?" Nicodemus asked. "Surely they cannot enter a second time into their mother's womb to be born!" 5 Jesus answered, "Very truly I tell you, no one can enter the kingdom of God without being born of water and the Spirit. 6 Flesh gives birth to flesh, but the Spirit gives birth to spirit. John 3
If your faith has left you cold then maybe you too need to be "born again". Ask Jesus to fill you with his Spirit and transform you. And then be sure to make room for him. Set your attention on things of God and not chasing after merely satisfying your wants and desires.
If you have any questions about this be sure to ask me because it's very important! Download Sunday's message here...Aquila, Priscilla & Apollo