The date for Easter was controversial was because both sides were arguing over which date was more biblical. No one was arguing in the early 2nd century that the church has authority to impose practices and observances that are not imposed in Scripture.
I found this comment striking because it is precisely dead wrong, and its dead-wrong-ness helps to illustrate precisely the opposite point from the one Dr. Clark was attempting to make. In actuality, no one in the Easter controversy was arguing that their date was more biblical. They knew better than to try that, since it is obvious that the feast of Easter isn't even mentioned in the Bible. Rather, each side was arguing their position from an alleged unwritten tradition coming from the apostles. One side cited the practice of the Apostle John, and the other side cited a different tradition (perhaps one stemming from Peter and Paul in Rome). Dr. Clark thinks that no one in the early 2nd century (actually, this controversy took place in the late 2nd century) believed that the Church had the authority to "impose practices and observances that are not imposed in Scripture." But, actually, everyone believed that, and this controversy illustrates it. No one in this controversy, so far as we have any record of, advocated a Sola Scriptura approach to the issue, or (as Dr. Clark and other Reformed theologians would have done had they been there) objected to the whole controversy as wrongheaded because of its lack of a biblical foundation. This shows well just how absent the idea of Sola Scriptura was from the consciousness of the entire Church just one hundred years or so after the days of the apostles. The early Church was Catholic in its view of Scripture, Tradition, and Church authority, not Protestant.
I'll close with a couple of quotations from two early Fathers--St. Basil of Caesaria and St. Vincent of Lerins--which articulate the Catholic view of the early Church, a view which continues to be articulated by the Catholic Church today.
Of the beliefs and practices whether generally accepted or publicly enjoined which are preserved in the Church some we possess derived from written teaching; others we have received delivered to us "in a mystery" by the tradition of the apostles; and both of these in relation to true religion have the same force. And these no one will gainsay—no one, at all events, who is even moderately versed in the institutions of the Church. For were we to attempt to reject such customs as have no written authority, on the ground that the importance they possess is small, we should unintentionally injure the Gospel in its very vitals; or, rather, should make our public definition a mere phrase and nothing more. For instance, to take the first and most general example, who is thence who has taught us in writing to sign with the sign of the cross those who have trusted in the name of our Lord Jesus Christ? What writing has taught us to turn to the East at the prayer? Which of the saints has left us in writing the words of the invocation at the displaying of the bread of the Eucharist and the cup of blessing? For we are not, as is well known, content with what the apostle or the Gospel has recorded, but both in preface and conclusion we add other words as being of great importance to the validity of the ministry, and these we derive from unwritten teaching. Moreover we bless the water of baptism and the oil of the chrism, and besides this the catechumen who is being baptized. On what written authority do we do this? Is not our authority silent and mystical tradition? Nay, by what written word is the anointing of oil itself taught? And whence comes the custom of baptizing thrice? And as to the other customs of baptism from what Scripture do we derive the renunciation of Satan and his angels? Does not this come from that unpublished and secret teaching which our fathers guarded in a silence out of the reach of curious meddling and inquisitive investigation? (St. Basil of Caesaria, On the Holy Spirit, Chapter 27--from the New Advent website, embedded links removed)
But here some one perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join with it the authority of the Church's interpretation? For this reason—because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another; so that it seems to be capable of as many interpretations as there are interpreters. For Novatian expounds it one way, Sabellius another, Donatus another, Arius, Eunomius, Macedonius, another, Photinus, Apollinaris, Priscillian, another, Iovinian, Pelagius, Celestius, another, lastly, Nestorius another. Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for the right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation. (St. Vincent of Lerins, Commonitory, Chapter 2--from the New Advent website, embedded links removed)
For more, see here and here.
Published on the feast of St. Benedict.