ROB TURNER
When playing repertoire from before the later seventeenth century, everything must be articulated, but the articulation has to be subtle. Much instrumental repertoire in this period was originally written as vocal music with text, and that text can serve as a useful guide on how to apply articulations. Often a particular syllable spans several notes, so those notes should not be too separate, or you will end up with something a bit clunky and unintelligible (as, for instance, the word "un in tell i gi ble" doesn't make much sense if you enunciate TOO “clearly”). This is where a mix of stronger and weaker articulation syllables comes into play, as in tu-du, ti-di (ti-ri), di-dl, etc. Sometimes these articulation techniques result in passages that sound almost as if they are slurred, but at least through the middle of the seventeenth century every note receives some sort of send-off, however gentle, with the tongue.COMMENTS ON SLURRING
For high baroque music it's a different story. Music started being
published with explicitly indicated slurs in the 17th C., and by the end
of the century, in the music of Purcell, et al, slurring is an effective
(and affective) expressive device. Almost never are two notes separate
and equal (when it does occur, that has an expressive significance in itself!).