Pursuant to CLS 1961, § 479.20 (Stat Ann 1965 Cum Supp § 22.585), plaintiff filed complaint in Ingham county circuit court to appeal an order of Michigan public service commission requiring plaintiff to cease and desist from transporting cement, except as specifically authorized in plaintiff’s authority.1

The pertinent language of the order appealed from is as follows:

“It is therefore our finding that under the portion of Telischak’s authority complained of herein respondent may transport only commodities intended for use in the construction, repair and dismantling of pipelines and that such service is restricted to service for the oil and gas industries.

“It is also our finding that respondent may transport only commodities intended to be used directly in such construction, repair or dismantling and that such authority does not authorize transportation of commodities requiring an intermediate manufacturing process prior to such ultimate use.

“It is therefore ordered:

“(1) [This part of the order is not pertinent to decision.]

“(2) That respondent, Telischak Trucking, Inc., be and the same is hereby ordered to cease and desist *27from the transportation of cement except as specifically authorized, in its authority.”

The trial court judgment affirmed the order of the commission except as to “such service is restricted to service for the oil and gas industries”, and restrained the commission from enforcing that part of its order not affirmed. Under the statute cited above, plaintiff appeals such affirmance. No one appeals that part of the judgment which restrains the commission from enforcing its order restricting service to the oil and gas industries.

The proceedings before the commission which resulted in the order appealed from were instituted on complaint of intervening defendants that plaintiff was hauling illegally bulk cement from Essexville, Michigan, to Flint. The consignees in Flint were 2 Catsman companies, one of which manufactured cement pipe, among other products, but neither of which was engaged in the construction or dismantling of pipelines. Although plaintiff has other certificates of convenience and necessity specifically authorizing transport of bulk cement from Monroe county and from Wyandotte to other points in Michigan, it has no authority to haul bulk cement from Essexville to Flint unless such authority is found -in the language quoted in footnote 1, supra. Plaintiff purchased the certificate which contains this language in 1955 but hauled no bulk cement under it until August 1963.

The statute under which plaintiff filed its complaint provides in part:

' “In all actions under this section the burden of proof shall be upon the complainant to show by clear and satisfactory evidence that the order of the commission complained of is unlawful or unreasonable, as the case may be.”

*28The Supreme Court said in Giaras v. Michigan Public Service Commission (1942), 301 Mich 262, 269:

“To declare an order of the commission unlawful there must be a showing that the commission failed to follow some mandatory provision of the statute or was guilty of an abuse of discretion in the exercise of its judgment.”

This test was reiterated in Bejin Cartage Company v. Public Service Commission (1958), 352 Mich 139, and in City of Ishpeming v. Public Service Commission (1963), 370 Mich 293. The inquiry then is, has plaintiff met the statutory burden?

Instead of advancing clear and satisfactory proof that the order complained of is unreasonable, plaintiff argues that the only limitation in its certificate is a commodity limitation and that by application of the “intended use rule” employed by the Interstate Commerce Commission in interpreting its certificates to the language of plaintiff’s certificate here involved, the plain and unambiguous meaning of the latter is that plaintiff may transport commodities which are used as pipe construction materials to any point in Michigan if it is demonstrated that such materials are pipe construction materials.

Assuming that the only limitation in plaintiff’s certificate is a commodity limitation, the foregoing argument fails because it ignores some essential language in the Interstate Commerce Commission’s description of the intended use rule. In Great Western Motor Lines, Inc., and Eugene G. Sharp—Investigation of Operations and Practices (1964), 96 MCC 522, 526, the commission said:

“Basically, the test is rather simple. Commodity descriptions governed by the test are those which identify the commodities authorized to be trans*29ported by reference to their intended future use. Strictly speaking, under the test, only those commodities specified in the description which are intended, at the time of movement, for use in the particular type of activity, enterprise, or place specified in the description and which, at the time of movement are, without further processing or manufacturing in a form and condition to he so used, may be transported.”

Here, at time of movement of bulk cement from Essexville to Flint, the commodity was not in a form for use as “pipe and pipeline laying and construction materials, supplies, equipment and machinery, incidental to or used in connection with the construction, repairing or dismantling of pipelines” without further processing or manufacturing.

In addition, a reading of all the language of the authority here in issue convinces us that the Michigan public service commission’s finding that plaintiff may transport only commodities intended to be used directly in such construction, repair, or dismantling and that such authority does not authorize transportation of commodities requiring an intermediate manufacturing process prior to such ultimate use is not unreasonable, but is rather the most reasonable finding on this record.

The only possible showing that the order is unlawful is plaintiff’s argument that in effect the order of the commission altered or modified its certificate and such alteration or modification is only possible by proceeding under CL 1948, § 479.18 (Stat Ann § 22.583), and the proceedings here were brought under CL 1948, § 479.14 (Stat Ann § 22.579). The argument is untenable for the reason its validity depends on the assumption that plaintiff’s certificate contains authority which Michigan public service *30commission, the trial court and this Court have found is not contained in such certificate.

Affirmed, with costs to defendants and intervening-defendants.

(dissenting). Telischak contends that the certificate of authority contains “a commodity description and not a job site delivery restriction,” and invokes the “intended-use” test utilized by the interstate commerce commission in interpreting commodity descriptions. (Emphasis supplied.) The attorney general for the commission asserts the “findings of the defendant commission that the transportation of cement under this certificate is subject to a construction site limitation cannot be said to be illogical or irrational.”1 (Emphasis supplied.) The intervening defendants assert the certificate contains a “commodity description restriction and also a construction site restriction.”

On appeal the circuit judge affirmed the commission on the ground that the record showed that only a portion of the cement delivered by Telischak to the consignees ultimately found its way into pipelines.2 The majority now affirm the circuit judge on the ground that Telischak failed to advance clear and satisfactory evidence showing the order of the commission is unreasonable, that under the intended-*31use test the commodity transported must at the time of transportation he in a form and condition so that it can be used without further processing or manufacturing, and that the commission’s interpretation is “the most reasonable finding on this record.”

The statute provides:

“In all actions under this section the burden of proof shall be upon the complainant to show by clear and satisfactory evidence that the order of the commission complained of is unlawful or unreasonable, as the ease may be.” CL 1948, § 479.20 (Stat Ann 1968 Cum Supp § 22.585).

There are no reported Michigan cases concerning the standard by which we review an order of the commission interpreting one of its certificates. The attorney general asserts the commission’s construction is controlling unless clearly erroneous, arbitrary, an abuse of discretion, or in contravention of some established principle of law, and that the judicial function is exhausted when it is found there is a rational basis for the conclusions of the commission, citing Whitehouse Trucking, Inc., v. United States (ND Ohio, 1966), 261 F Supp 9; Mitchell Brothers Truck Lines v. United States (Or, 1963), 225 P Supp 755 (15 P Carr Cases, § 81.595); and Ace Lines, Inc., v. United States (SD Iowa, 1960), 197 P Supp 591.

The commission has not, however, stated the reason3 for its decision, and thus we have no basis for *32determining whether the commission’s order is soundly based. The commission merely states its

“opinion that even if such authority * * * includes transportation of commodities for use in industries other than the oil and gas industries that Telischak would be authorized to transport only commodities intended to be used4 directly in the construction, repair or dismantling of pipelines.

“Clearly, such authority does not authorize the transportation of raw commodities requiring an intermediate manufacturing process prior to their use in such operations.”

If it is clear, it should be possible to state why it is clear. If it is clear, it should be possible to state whether it is clear because the certificate contains a commodity description which under the intended-use test, if adopted by the commission, requires or authorizes that result, or because the certificate contains a job site restriction, or because of some other reason.

It is not our task to guess whether the commission interprets the certificate before us as containing a “commodity description,” whether it in fact applied the IOC’s “intended-use” test in deciding that Telischak’s certificate does not authorize transportation of commodities requiring an intermediate manufacturing process prior to ultimate use, or whether it regarded the certificate as containing a “construction site” limitation (as the attorney gen*33eral asserts), or both a commodity description and a construction site limitation (as intervening appel-lees urge). Nor is it onr function to attempt to apply the ICC’s intended-use test before we know whether or how the commission would apply it.

The majority underscores the portion of Great Western Motor Lines, Inc. and Eugene G. Sharp-Investigation of Operations and Practices, 96 MCO 522, stating the requirement that the commodity be in a form and condition to be used without further processing or manufacturing, while the attorney general in his brief underscores the word “place” in that statement. In contrast, Telischak asserts that the cement it seeks to transport can be used for the “construction” of pipelines (in the sense of manufacturing pipe for pipelines, as contrasted with mere assembly of pipe already manufactured) without further processing or manufacturing of the cement. The commission states that Telischak is authorized to transport commodities intended to be used “directly” in the construction, repair, or dismantling of pipelines. The attorney general and intervening appellees say Telischak may transport cement to a site where a pipeline is being assembled. This perhaps explains the relevance of the commission’s statement that “the consignee companies do not engage in the so-called continuous pour pipeline operation and do not engage in any operations at the site of pipeline construction.” If, as appears to be the case, cement can be transported for use at the site where a pipeline is fabricated or assembled, then it may be that it is not the nature of the “intermediate manufacturing process” but the place where it occurs that is critical.

In construing one of its certificates the commission acts in a quasi-judicial capacity, not in a legislative *34capacity.5 Apart from its obligation to make findings of fact, the commission has an obligation to state the reasons for its conclusions. It is not our function to search for rational support of the commission’s order as we would if the constitutionality of a statute were under attack.6 It is rather for the commission to tell us why it reached the conclusion it did and for us then to decide whether that explanation, not one which we divine, is reasonable and according to law. To affirm the commission on a rationale not advanced by the commission would be just as much an invasion of the commission’s prerogative as to substitute our judgment for that of the commission where it advances a sound explanation for its interpretation.

The importance of requiring a statement of reasons in support of the commission’s conclusion is well illustrated by this case. The bulk of the commission’s opinion in this case is devoted to a demonstration that the certificate is a Mercer-type authority (T. E. Mercer Extension Oil Field Commodities, 74 MCC 459), and that, accordingly, Telischak may only transport commodities intended for use in the construction, repair, and dismantling of oil and gas pipelines. On appeal, the circuit judge reviewed decisions regarding the Mercer doctrine, concluded that Telischak’s certificate was not of that type, and, therefore, struck the portion of the opinion and order restricting Telischak “to service for the oil and gas industry.” No appeal has been taken from that portion of the circuit judge’s decision. Had *35the commission not articulated its view that this was a Mercer-type certificate, would we have been justified in searching for a rationale to justify the commission’s otherwise Delphic determination? I think not. Had we, nevertheless, done so, would we assuredly have understood from a commission opinion devoid of explanation that the result reversed by the circuit judge rested on the Mercer doctrine? I think not.

In Securities & Exchange Commission v. Chenery Corporation (1943), 318 US 80 (63 S Ct 454, 87 L Ed 626), the court, prior to the enactment of the Federal administrative procedure act,7 ruled that (1) an administrative tribunal may not be affirmed on a ground other than the ground on which it exercises its discretion because to do so would invade the authority vested in the administrative tribunal, and (2) in order to make effective judicial review possible, the administrative tribunal must disclose the reasons for its decision. The court observed (pp 88, 93, 94, 95):

“If an order is valid only as a determination of policy or judgment which the agency alone is authorized to make and which it has not made, a judicial judgment cannot be made to do service for an administrative judgment. For purposes of affirming no less than reversing its orders, an appellate court cannot intrude upon the domain which congress has exclusively entrusted to an administrative agency. * * *

“Its action must be measured by what the commission did, not by what it might have done. It is not for us to determine independently what is ‘detrimental to the public interest or the interest of investors or consumers’ or ‘fair or equitable’ within the meaning of sections 7 and 11 of the public utility holding company act of 1935. The commission’s *36action cannot be upheld merely because findings might have been made and considerations disclosed which would justify its order as an appropriate safeguard for the interests protected by the act. * * *

“The orderly functioning of the process of review requires that the grounds upon which the administrative agency acted be clearly disclosed and adequately sustained. * * *

“We are not suggesting that the commission must justify its exercise of administrative discretion in any particular manner or with artistic refinement. We are not sticking in the bark of words. We merely hold that an administrative order cannot be upheld unless the grounds upon which the agency acted in exercising its powers were those upon which its action can be sustained.”

Several years later Chenery returned to the Supreme Court, Securities & Exchange Commission v. Chenery Corporation (1947), 332 US 194, 196, 197 (67 S Ct 1575, 1577, 91 L Ed 1995, 1999). The Court referred to its earlier holding and declared:

“When the case was first here, we emphasized a simple but fundamental rule of administrative law. That rule is to the effect that a reviewing court, in dealing with a determination or judgment which an administrative agency alone is authorized to make, must judge the propriety of such action solely by the grounds invoked by the agency. If those grounds are inadequate or improper, the court is powerless to affirm the administrative action by substituting what it considers to be a more adequate or proper basis. To do so would propel the court into the domain which congress has set aside exclusively for the administrative agency.

“We also emphasized in our prior decision an important corollary of the foregoing rule. If the administrative action is to be tested by the basis upon which it purports to rest, that basis must be set forth with such clarity as to be understandable. It *37will not do for a court to be compelled to guess at the theory underlying the agency’s action; nor can a court be expected to chisel that which must be precise from what the agency has left vague and indecisive. In other words, 'We must know what a decision means before the duty becomes ours to say whether it is right or wrong.’ United States v. Chicago, M. St. P. & P. R. Co. (1935), 294 US 499, 511 (55 S Ct 462, 467, 79 L Ed 1023, 1032).”

Professor Davis explains the judicially imposed requirement that administrative agencies state reasons is a by-product of the process of judicial review, and a court which is reviewing an administrative action often feels the need for a statement of reasons in order to better understand what it is reviewing. 2 Davis, Administrative Law Treatise, § 16.12, p 477.

It has been said:

“If judicial review is to have a basis for functioning, the ICC must do more than announce its ultimate conclusions by way of unrationalized fiat. The commission must explain its reasoning in clear and precise terms.” Florida East Coast Railway Company v. United States (MD Fla, 1966), 259 F Supp 993, 999. (Emphasis supplied.) See, also, D. M. K. Realty Corp. v. Gabel (1963), 40 Misc 2d 89 (242 NYS2d 517); Northeast Airlines, Inc., v. Civil Aeronautics Board (CA 1, 1964), 331 F2d 579.

While the Michigan public service commission is exempted from our administrative procedure act (CLS 1961, §24.101 [Stat Ann 1961 Eev §3.560 (21.1)]), it is subject to the judicially imposed requirement that it state reasons for decision. Unless the commission does so, we cannot provide that measure of review required by the Constitution (Const 1963, art 6, § 28) and the statute (CLS 1961, §479.20, Stat Ann 1968 Cum Supp § 22.585). Un*38less the commission states reasons, we are left to guess what they might be, or to rationalize reasons of our own, reasons which the commission might itself reject. To affirm on the basis of a reason which the commission itself might not adopt would be to invade the commission’s function. This we should avoid. And we have no way of knowing whether the commission has adopted a particular reason unless it tells us whether it has.

Our job is to review reasons advanced by the commission, not to select amongst the competing reasons postulated by counsel for the parties, nor attempt to understand tests evolved by the United States interstate commerce commission which may or may not have been adopted by the Michigan public service commission,8 and to search out a plausible basis for the commission’s action.

I would reverse and remand to the commission for clarification of its opinion.