The Apostles were the beginning of the Magesterium.
As you can see, people can read a single, seemingly simple passage, and disagree on the interpretation of it. (Hence, the tragic growth in the number of Prot. denominations.) At some point, there needs to be an Authority. The Father sent the Son. The Son sent the Apostles. We Catholics trace our ties back to these men, and our Magesterium are their apostolic successors.
The only other solution is to flip a coim, hmmm - shall we believe Pastor X or Pastor Y or even Diego1618. It may be hard for you to believe, but there are men more wise and learned on Scripture and Theology than you, or even I. I worship in Peter's Church, not Diego1618's.
Then I'm sure you would not mind giving me your take on Matthew 28:1?????
Please read to see the real scoop about the number of Protestant denominations:
http://www.ntrmin.org/30000denominations.htm
Please note. If you have issues with this article, it is a review of World Christian Encyclopedia: A Comparative Survey of Churches and Religions in the Modern World A.D. 1900—2000 (ed. David A. Barrett; New York: Oxford University Press, 1982). The Barrett article is the source of the 20,000+ Protestant denominations often cited by Catholic apologists. If you don't like his conclusions, then please stop claiming 20,000+ denominations.