¶ 109. (dissenting). I agree with the majority's conclusion that Wis. Stat. § 973.09(3)(a) does not provide statutory authority for a circuit court to reduce the length of probation. I write separately, however, to address the issue of inherent authority because I conclude that Dowdy did not forfeit his right to have this court address that issue.
¶ 110. No party disputed that a circuit court has the inherent authority to reduce the length of probation. The issue is not whether the court has such authority. It does. Rather, the issue is what are the parameters of that authority.
¶ 111. A circuit court must exercise its inherent authority within "defined parameters." State v. Crochiere, 2004 WI 78, ¶ 12, 273 Wis. 2d 57, 681 N.W.2d 524. Although the parties agree that the court has inherent authority, they disagree about the proper standard for the circuit court's inherent authority to reduce the length of probation. Dowdy advocates for the "cause" standard. By contrast, the State asserts that the circuit court's inherent authority to reduce the length of probation should be limited in the same way that a *607circuit court's inherent authority to reduce a sentence is limited — in this case, based on the presence of a "new factor."1 Upon close examination, both of these standards are problematic.
¶ 112. I am not persuaded that Dowdy's proposed standard, "cause," sufficiently circumscribes the court's exercise of inherent authority. Rather, the "cause" standard begs the question. If a circuit court can reduce the length of probation for cause, what constitutes cause to reduce the length of probation?
¶ 113. According to the court of appeals, "the law places no limitation on what the trial court may consider as cause" when extending probation under Wis. Stat. § 973.09(3)(a). State v. Edwards, 2003 WI App 221, ¶ 14, 267 Wis. 2d 491, 671 N.W.2d 371. I fear that such an amorphous standard would provide insufficient guidance to circuit courts.
¶ 114. Likewise, I am not persuaded that the State's "new factor" standard, which is transposed wholesale from the standards for sentence modification, is workable in the context of probation modification. The purposes of sentencing and probation are distinct, and the distinction makes a difference.
¶ 115. There are several purposes of imposing a criminal sentence, only one of which is the defendant's rehabilitation. See C.J. Abrahamson's dissent, ¶ 97. By contrast, the dual purposes of imposing probation are "to protect the public from criminal conduct and to help *608the probationer become a useful member of society." Wagner v. State, 89 Wis. 2d 70, 77, 277 N.W.2d 849 (1979). Both purposes of probation have been served when a probationer has been rehabilitated. When a probationer becomes a useful member of society, he or she has been rehabilitated, and the public is protected from criminal conduct.
¶ 116. Because rehabilitation is so essential to the court's purpose for imposing probation in the first instance, a circuit court should be able to consider whether a defendant has been rehabilitated when deciding a motion to reduce the length of probation. Accordingly, we have stated that "[probation modification provides the circuit court with a means of rewarding post-sentencing rehabilitation . . . ." State v. Kluck, 210 Wis. 2d 1, 9, 563 N.W.2d 468 (1997).
¶ 117. However, our case law makes clear that, for purposes of sentence modification, a defendant's post-sentencing rehabilitation cannot be considered a new factor. Id. at 7-8. Thus, if we were to accept the State's proposed standard and adopt the sentence modification parameters wholesale, we would significantly undermine the circuit court's inherent authority by preventing the circuit court from considering rehabilitation, the underlying purpose of probation.
¶ 118. Accordingly, I conclude that neither of the standards offered by the parties is suited to define the parameters of the circuit court's exercise of inherent authority. One standard is too broad, providing virtually no definition to guide the court, and the other is too narrow, appearing to render the court's inherent authority illusory. The parties' proposed standards provide no middle ground.
¶ 119. I conclude that a third alternative is necessary. This is an important issue that affects the lives *609of a multitude of people and the administration of justice. This court should craft a standard that is sufficiently defined to provide parameters for the circuit court's inherent authority, but that would allow the circuit court to take into account the defendant's rehabilitative progress in some fashion when determining whether probation reduction is warranted.
¶ 120. For the reasons fully set forth by the Chief Justice, I conclude that Dowdy did not forfeit the inherent authority issue. See C.J. Abrahamson's dissent, ¶¶ 52-71. Because I think it would be unwise for this court to craft, sua sponte, a new standard without further input from the parties, I would request supplemental briefing about the proper standard for the circuit court's exercise of inherent authority. Accordingly, I respectfully dissent.
In addition to its inherent authority to modify a sentence when a "new factor" is presented, a circuit court may exercise its inherent authority to modify a sentence to correct formal or clerical errors, to correct an illegal or void sentence, or to modify an unduly harsh or unconscionable sentence. State v. Crochiere, 2004 WI 78, ¶ 12, 273 Wis. 2d 57, 681 N.W.2d 524.