My instinct would be to say that Buddha, Dharma, and Sangha are the triple gem, and that is that. But the question left me with some unease.
For one, when Koṇḍañña became the first bhikkhu, if I am not mistaken, the Historical Buddha asked him to take refuge in the Buddha and the Dharma but not the Sangha, because there was no Sangha yet. Thus, can it be said that the in some way the Triple Gem was once (however fleetingly) the "Double Gem"?
Then I came across this quote by one Prof. Jikido Takasaki:
Thus seems to suggest some sort of "primacy" involving the two.[the f]undamental structure of Buddhism may be summarized in the following way: The Buddha, having realized the Dharma by himself, preached the Dharma for the sake of others. The Dharma realized by the Buddha through introspection is said to be the law of causation (pratityasamut pada), which is explained through Buddha's voice in the form of the four aryasatyas and others.
In this structure, the ultimate value in Buddhism is fundamentally the Dharma, the truth, and the Buddha is merely a mediator who conveyed the truth to the people by means of words understandable to them. As for the religious feeling, however, the Buddha is considered to be the ultimate value, the object of worship, since he is the law-giver and the practical ideal in the sense that one should attain Enlightenment (bodhi) (i. e. to become buddha) through Buddha's instruction, the Dharma. Thus the Buddha is the first of the triratna, and the Dharma comes the second, which is used to be interpreted as the Buddha's inst ruction (buddhasasana) of which the authority is in the Buddha himself. But, again, the Buddha's authority lies in the belief that the Buddha revealed the truth, and on this belief the Buddha is called tathāgata, thus gone or come, which is interpreted as having become one with the truth or reality (tathata).
Then there are the arcane mysteries of the Dharmadatu, Dharmakaya, and Tathagatagharba, which may or may not have some bearing on the issue.
Thoughts?