I agree with your conclusion that the traditional distinction between Classical and Late Biblical Hebrew becomes unstable if Isaiah 40-66 is dated to the post-exilic period. The language of Isaiah 40-66 is indeed “anchored well” (Hurvitz) in Classical Biblical Hebrew. Where you and I differ is that I, with Young, Ehrensvärd, and others, regard the CBH/LBH dichotomy itself as already theoretically and methodologically unstable.
With respect to II(-III) Isaiah, I consider this material -- on the basis of historical, theological, and other criteria -- to have been composed in the exilic/post-exilic period, in line with the critical consensus. Accordingly, I view its language as a prime specimen of exilic/post-exilic Classical Biblical Hebrew. (See further my unpublished discussion here: https://www.academia.edu/25885221/2016k_Rezetko_Response_to_Rooker_Char….)
All of this, however, raises uncomfortable questions that cut in both directions and run counter to various forms of scholarly consensus. Scholars have long recognized the dilemma, and more recently some have attempted to account for the language of Isaiah 40-66 by classifying it as “Transitional Biblical Hebrew.” Yet, as you have hinted, this explanation is also unsatisfactory. Moreover, the very notions of Transitional Biblical Hebrew and “transitional language” more generally are themselves deeply problematic, both theoretically and empirically. (See further https://www.sbl-site.org/wp-content/uploads/2025/01/9781628370461_OA.pdf, esp. pp. 395-402; https://jhsonline.org/index.php/jhs/article/view/29350/21370, esp. pp. 29-38.)
I agree with your conclusion that the traditional distinction between Classical and Late Biblical Hebrew becomes unstable if Isaiah 40-66 is dated to the post-exilic period. The language of Isaiah 40-66 is indeed “anchored well” (Hurvitz) in Classical Biblical Hebrew. Where you and I differ is that I, with Young, Ehrensvärd, and others, regard the CBH/LBH dichotomy itself as already theoretically and methodologically unstable.
With respect to II(-III) Isaiah, I consider this material -- on the basis of historical, theological, and other criteria -- to have been composed in the exilic/post-exilic period, in line with the critical consensus. Accordingly, I view its language as a prime specimen of exilic/post-exilic Classical Biblical Hebrew. (See further my unpublished discussion here: https://www.academia.edu/25885221/2016k_Rezetko_Response_to_Rooker_Char….)
All of this, however, raises uncomfortable questions that cut in both directions and run counter to various forms of scholarly consensus. Scholars have long recognized the dilemma, and more recently some have attempted to account for the language of Isaiah 40-66 by classifying it as “Transitional Biblical Hebrew.” Yet, as you have hinted, this explanation is also unsatisfactory. Moreover, the very notions of Transitional Biblical Hebrew and “transitional language” more generally are themselves deeply problematic, both theoretically and empirically. (See further https://www.sbl-site.org/wp-content/uploads/2025/01/9781628370461_OA.pdf, esp. pp. 395-402; https://jhsonline.org/index.php/jhs/article/view/29350/21370, esp. pp. 29-38.)